An Agenda-Setting Theory of Electoral Competition Tiberiu Dragu, New York University Xiaochen Fan, New York University The strategy of parties regarding which issues to emphasize during electoral campaigns is an important aspect of electoral competition. In this article, we advance research on electoral competition by developing a multidimensional model of electoral competition in which parties compete for electoral support by raising the electoral salience of position issues. We show that parties have incentives to advertise an issue on which the opponent has a more popular position or an issue on which neither party has electoral advantage. We also show that the party with the lower equilibrium vote share prefers to emphasize more controversial issues, while the party with the higher equilibrium vote share prefers to emphasize more consensual issues on its electoral agenda. The analysis provides a theoretical foundation for moving toward a more complete understanding of the content of campaign communication on issues on which voters disagree about which policies ought to be implemented. It also provides novel empirical predictions about how the structure of public opinion impacts the campaign strategy of parties, which can foster further empirical research on electoral campaigns and issue selection.

T

he strategy of parties regarding which policy issues to emphasize during electoral campaigns is an important aspect of electoral competition. An extensive literature shows that parties selectively emphasize various policy issues in order to sway citizens to put more weight on those considerations when casting their votes (Druckman, Jacobs, and Ostermeier 2004; Iyengar and Kinder 1987; Riker 1996). As Donald Stokes (1963, 372) noted, “The skills of political leaders . . . consist partly in knowing what issue dimensions . . . can be made salient by suitable propaganda.” Such strategizing over issue selection has been widely documented in numerous electoral contests in a variety of countries, including the United States, Canada, the United Kingdom, Spain, Germany, and Japan (Aldrich and Griffin 2003; Budge and Farlie 1983; Druckman, Kifer, and Parkin 2009; Laver and Hunt 1992; McCombs 2004; Ward et al. 2015). Since Stokes (1963) introduced the distinction between valence and position issues, scholars have made important theoretical and empirical advances in our understanding of

the determinants of issue selection, mostly in the context of valence issues (Aragones, Castanheira, and Giani 2015; Budge and Farlie 1983; Clarke et al. 2009; Egan 2013; Petrocik 1996).1 As scholars have argued, in reality, political issues have both valence and positional aspects since citizens have diverse views about how to achieve consensual goals (Clarke et al. 2009; Egan 2013; Laver 2001; Miller and Shanks 1996; Stokes 1963).2 However, the strategy of parties regarding which position issues to emphasize in electoral campaigns is relatively understudied. For example, we know little about how the structure of public opinion on various policy issues shapes the issue selection strategy of candidates. Do parties emphasize policy issues on which voters are more ideologically heterogeneous or ideologically homogeneous? Does a party advertise issues on which its opponent has electoral advantage or on which neither candidate has electoral advantage? What position issues are more likely to be bundled together on a party’s electoral agenda? To answer these questions, we develop a multidimensional model of electoral competition in which parties compete for

Tiberiu Dragu ([email protected]) is an assistant professor in the Department of Politics at New York University, New York, NY, 10012. Xiaochen Fan ([email protected]) is a clinical assistant professor in the Department of Economics at New York University, New York, NY, 10012. Data and supporting materials necessary to reproduce the numerical results in the paper are available in the JOP Dataverse (https://dataverse.harvard.edu /dataverse/jop). An online appendix with supplementary material is available at http://dx.doi.org/10.1086/686310. 1. Valence issues are defined as those issues on which there is “overwhelming consensus as to the goals of government action” (Stokes 1963, 373) and on which the electoral competition is about which party is better to deliver what everyone wants. In contrast, position issues are defined as those issues “that involve advocacy of government action from a set of alternatives over which a distribution of voter preferences is defined” (Stokes 1963, 373). 2. For instance, voters undoubtedly agree that low crime is a desirable objective; however, they might have different opinions whether we can attain it by imposing harsher penalties or by addressing socioeconomic inequalities. The Journal of Politics, volume 78, number 4. Published online August 3, 2016. http://dx.doi.org/10.1086/686310 q 2016 by the Southern Political Science Association. All rights reserved. 0022-3816/2016/7804-0015$10.00

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electoral support by raising the electoral salience of various position issues. In our framework, the players are two political parties and a continuum of voters; the parties and the voters have ideal policies in an n-dimensional policy space, and the distribution of voters’ ideal policies on the n policy issues is multivariate normal. Parties have fixed policy positions and compete over which issues are electorally important: each party chooses a vector of advertisements to raise the electoral salience of various issue dimensions in order to maximize its vote share minus the cost of issue advertisement. Each voter elects the party that is closer to his/her policy position on the n issues; the proximity between a voter’s and a party’s policy position on the n issues is an aggregate of the difference between the voter’s and the party’s preferred policy on each issue, weighted by the salience of each issue. The relative salience of each issue is endogenously determined by the parties’ campaign advertisement choices, and the salience vector determines the distribution of the electorate’s preference regarding which party is more electorally desirable. One might expect that a party wants to increase the salience of those issues on which a majority of voters prefer its policy position so as to augment its overall electoral popularity. This is indeed an important consideration of a party’s strategic calculus because promoting such issues increases a party’s vote share by making its policy position relatively closer to the center of the electorate on the n issues. However, increasing the salience of an issue also affects how concentrated/dispersed voter preferences are on the n issues. In other words, when a party chooses which issues to emphasize, its issue-selection strategy simultaneously impacts the equilibrium vote share through two channels: it changes a party’s electoral popularity, and it also changes the electoral heterogeneity regarding which party is more desirable. That electoral heterogeneity is an important factor for understanding the strategy of issue selection in electoral contests is missing from the existing literature. To illustrate how electoral heterogeneity shapes the issue selection incentives of parties, consider two policy issues that differ only in the variance of voter preferences. This implies that the electoral heterogeneity regarding which party is more desirable is higher on the issue on which the variance of voter preferences is higher. The party whose policy position is further from the center of the electorate does better on the issue with higher electoral heterogeneity since it can capture a higher number of voters in some tail of the distribution. On the other hand, the party whose position is closer to the center of the electorate, the party that has an electoral advantage, does better on the issue with lower electoral heterogeneity. As a result, the former party prefers to advertise the issue with higher heterogeneity, while the latter

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party prefers to emphasize the other issue. Accounting for these divergent incentives due to differences in electoral heterogeneity across policy issues allows us to uncover new theoretical results regarding what kinds of position issues a party is more likely to emphasize on its electoral agenda. We show that parties have incentives to advertise an issue on which the opponent has electoral advantage or an issue on which neither party has electoral advantage. This result underscores some limitations of Riker’s influential analysis of issue selection in electoral contests. Riker (1996) proposes two general principles of electoral campaigns: the dominance principle (a party does not advertise an issue on which the opponent has advantage) and the dispersion principle (if neither of the two parties has advantage on an issue, both parties ignore that issue). Our analysis suggests that these principles need not hold when we scrutinize the mechanisms by which increasing the salience of an issue affects a party’s vote share. We also show that the advertisement pattern of the minority party, the party with the lower equilibrium vote share, differs from the advertisement pattern of the majority party, the party with the higher equilibrium vote share, when we consider whether a party is more likely to advertise controversial or consensual issues (i.e., issues on which voters are more ideologically heterogeneous or more ideologically homogeneous). This result expands our understanding of how the strategies of political losers and winners shape the composition of policy agenda in electoral campaigns. Research on issue evolution and manipulation suggests that minority parties have incentives to publicize issues that are more likely to split the majority party’s electoral coalition, whereas the majority party has incentives to keep such issues off the electoral agenda (Carmines and Stimson 1989; Key 1955; Schattschneider 1960). This literature focuses on the dynamics of electoral coalitions; it essentially underscores variations in the issues advertised by one party relative to the issues advertised by the other party. Our result is substantively different in that our analysis underscores variations in advertisement among the issues that a party emphasizes on its electoral agenda. That is, the minority party puts more advertisement on controversial issues within the set of position issues on which it campaigns. In contrast, the majority party puts more emphasis on consensual issues within the set of position issues on its electoral agenda. These findings provide novel substantive insights into how the strategies of parties shape the composition of policy agenda during electoral contests. This article adds to a political economy literature on electoral competition. In the classic spatial approach to electoral competition, parties propose policy positions to maximize their electoral success, while voters choose the party

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closest to their policy preferences (Downs 1957). Scholars have complemented this spatial analysis by analyzing other important facets of electoral competition, including the effect of candidates’ nonpolicy characteristics on electoral competition (Forand 2014; Groseclose 2001; Krasa and Polborn 2010a, 2010b; Schofield 2007), the possibility of strategic entry by new parties (Callander 2005; Palfrey 1984), the effect of negative campaigning on electoral decisions (Polborn and Yi 2006; Skaperdas and Grofman 1995), the influence of party activists and campaign spending in elections (Baron 1994; Fox and Rothenberg 2011; Grossman and Helpman 1996), and the effects of alternative electoral systems on voter choice and party competition (Cox 1987). However, the question of issue selection is underresearched. This is problematic because, when we think about real elections, an important aspect of electoral competition—encapsulated in the perennial question “What was this election about?”—is what policy issues to emphasize and what policy issues to ignore. Our article provides a theoretical foundation for moving toward a more complete understanding of the content of campaign communication on issues on which voters disagree about which policies ought to be implemented. This article also contributes to a literature on how the strategic competition among political parties shapes issue agenda in elections (Riker 1986, 1996). The formal literature has analyzed the conditions under which certain policy issues remain on the electoral agenda (Glazer and Lohmann 1999), the conditions under which parties put forward new policy issues relative to the existing status quo (Colomer and Llavador 2012), the effect of media bias on the incentives of parties to publicize policy issues (Puglisi 2004), the conditions under which candidates emphasize valance issues on which they have an ex ante advantage when issue ownership is endogenously determined (Aragones et al. 2015), whether or not parties emphasize similar issues during electoral campaigns (Amorós and Puy 2013; Hammond and Humes 1995; Simon 2002), the manipulation of issue dimensions (Moser, Patty, and Penn 2009), and how changing the salience of issues can alter the winners in elections (Feld, Merrill, and Grofman 2014).3 Relative to existing formal models, our article shows a novel mechanism by which issue advertisement impacts a party’s vote share, which allows us to derive new theoretical results on the strategy of issue selec-

3. Also, Egorov (2012) studies a model of election with two candidates and two valence dimensions, where the candidates’ competence on each issue is an unobservable random variable; Ash, Morelli, and Van Weelden (2015) study how the choice of a common value or divisive issue on which to campaign can serve as a credible signal of an incumbent politician’s type.

tion.4 Understanding how increasing the salience of an issue affects the electoral heterogeneity regarding which party is more desirable also allows us to assess counterfactuals about which position issues are more likely to be emphasized if those issues differ in terms of the electoral advantage of parties or in terms of the ideological diversity of voters. Therefore our article also yields novel empirical predictions about how the structure of public opinion impacts the campaigning strategy of candidates, which can foster further empirical research on electoral campaigns and issue selection.

MODEL The players are a continuum of voters, whose measure is normalized to 1, and two political parties, A and B. The policy space is multidimensional: there are n issue dimensions, and the set of possible policy choices for each issue i (i p 1, 2, :::, n) is R. Each party k ∈ fA, Bg has an ideal policy, a vector pk p k k (p1 , p2 , :::, pkn ) ∈ Rn , where the i-th element denotes party k’s preferred policy on issue i. The parties’ most preferred policies on each issue dimension differ; that is, pAi ≠ pBi for all i. The focus of our model is to analyze how parties compete for votes by raising the salience of various issues, and thus we assume the parties’ policy positions to be fixed for the duration of the campaign.5 Each voter has an ideal policy vector x ∈ Rn . The location of the voters’ ideal policies follows a multivariate normal distribution, and the voters’ positions on various issue dimensions are uncorrelated. That is, a generic voter’s ideal ! " policy is xn#1 ∼ N mn#1 , on#n with jij p 0 for any i ≠ j, where jij is the (i, j)-th element of Σ. We focus on the situation in which voters’ policy positions are uncorrelated because it allows us to investigate the effect of the structure of various policy issues on parties’ campaign strategies in a simple 4. The few existing formal models of (position) issue selection typically analyze the problem of issue selection in a setting in which there is a representative voter (Egan 2013; Simon 2002) or in a two-policy issue space where the total amount of resources allocated to issue advertisement needs to satisfy a budget constraint (Amorós and Puy 2013; Simon 2002). Questions such as whether parties are more likely to emphasize controversial or consensual issues are not addressed by these existing models. 5. Fixed policy positions can be due to a previous electoral stage that is not modeled here. The existing theoretical literature suggests several factors as to why the policy platforms of parties differ when they enter the general electoral competition, including the influence of party activists (Baron 1994) and the influence of internal bargaining and nomination processes (Coleman 1971). The existing literature also shows empirical evidence that voter perceptions regarding the parties’ positional images are stable over time (Dalton and McCallister 2015) and also that voters do not systematically adjust their perceptions of parties’ positions in response to shifts in policy statements during election campaigns (Adams, Ezrow, and SomerTopcu 2011).

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manner. The assumption is consistent with existing empirical evidence. Since Converse (1964) famously documented that the public shows very little ideological constraint across different policy issues, the empirical evidence has supported the finding of low ideological consistency across separate policy issues (Fiorina, Abrams, and Pope 2005; Kinder and Sears 1985; Zaller 1992). Low ideological consistency, of course, is more likely to be the case among those voters who do not have partisan attachments and thus could be persuaded by the parties’ campaign messages, the electorate that is the focus of our model, as discussed momentarily. Moreover, in an extension of the model in the appendix, available online, we also analyze the situation in which voter preferences across issues are correlated (i.e., jij ≠ 0 for i ≠ j) to show that the main results are robust to this extension. In our framework, each issue dimension can thus be characterized in terms of (mi, jii), the mean and the variance of the distribution of voters’ ideal policies on policy issue i, where jii is the i-th diagonal element of Σ. Thus the pair (mi, jii) can be thought of as characterizing the existing public opinion on policy issue i. Given the existing public opinion on various policy issues, each party k ∈ {A, B} chooses an amount of advertisement for each issue dimension, a vector ak p (ak1 , ak2 , :::, akn ) ∈ Rn1 n at a cost Ck (ak ) p oip1 ck (aki ). The campaign advertisement can be thought as the amount of money, time, and effort parties allocate to emphasize certain policy issues during electoral campaigns in order to persuade voters that those issues are a governing priority. We assume that the cost function is twice 0 00 continuously differentiable, c k (⋅) 1 0, c k (⋅) 1 0, c k(0) p 0, 0 0 c k (0) p 0, lima→∞ c k (a) p ∞ and lima→∞ c k (a) p ∞ for k ∈ {A, B}.6 The objective of each party is to maximize the vote share less the cost of issue advertising. Thus, party k’s utility is U k (ak ; a2k ) p v k (ak ; a2k ) 2 Ck (ak ), where ak is the vector of advertisement on the n issues by party k and v k is party k’s vote share, which will be characterized in the next section. A voter’s preference over policies depends on the difference between the implemented policy and his/her ideal policy on each issue and on the relative importance the voter

6. The focus of our model is to analyze the strategy of issue advertisement in campaigns. However, during electoral campaigns, candidates devote resources to other activities, such as hiring staff, polling, analyzing data, and developing ground organizations that can be crucial for the turnout of voters and core constituency. As such, the cost of issue advertisement can be thought as an opportunity cost.

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puts on each policy issue. Thus the utility of a voter with ideal policy x is n

U v p 2 o wi (a)( pi 2 xi )2 , ip1

ð1Þ

where a p (aA , aB ) and wi (a) represents the relative importance the voter puts on issue i for i p 1, 2, ::: , n. The electoral salience of various policy issues is affected by the parties’ issue advertisement. Specifically, for each issue i denote by ai p ok aki the total amount of advertisement issue i receives in an electoral campaign. Because the relative importance of each issue depends on the total advertisement of that respective issue, we can re-express the vector of advertisement on the n issues as a p (a1 , a2 , :::, an ). The issue salience vector then is a function of the parties’ advertisement strategy: w(a) p fwi (a)gnip1 . We assume that wi (a) p f (ai )= n oip1 f (ai ), where f(⋅) is an increasing twice continuously differentiable function and f (x) 1 0 for all x and therefore n oip1 wi (a) p 1.7 The contest success function wi (a) encapsulates how the parties’ campaign advertisement effort to highlight which issues are more important translates into the voters’ assessments regarding the relative salience of various policy issues. We take a reduced-form model of this process because our main interest is to investigate the issue-selection incentives of the parties.8 Our approach here is similar to other papers that use contest functions to model how campaign advertisement and spending affect the behavior of voters (Baron 1994; Grossman and Helpman 1996); Skaperdas and Grofman 1995; Snyder 1989). The contest success function can be derived from axiomatic theories of (partially) uninformed voting Luce 1959, from an inferential process of an (uninformed) audience that observes evidence produced by contestants who seek to persuade the audience of the correctness of their views (Skaperdas and Vaidya 2012), or from a political contest in which parties provide costly information to voters (Gul and Pesendorfer 2012). More importantly, the key assumption of contest function wi (a) that if an issue receives more advertisement than others, the relative electoral importance of that policy issue is higher has garnered significant empirical support. An extensive empirical literature documents that the amount of media ! n " 7. Examples of such functions are: wi (a) p (ai 1 a)= oip1 ai 1 na , ! n " n 2 2 ai ai a 1 0; wi (a) p (ai 1 a)= oip1 ai 1 na , a 1 0; wi (a) p (e )=oip1 e ; n and wi (a) p log (ai 1 a)=oip1 log (ai 1 a), a 1 1. 8. In this sense, this article is related to other models of electoral competition which analyze the strategic behavior of candidates given various notions of voting behavior (Adams 2001; Adams, Merrill, and Grofman 2005; Bendor et al. 2011; Callander and Wilson 2008; Diermeier and Li 2013).

1174 / An Agenda-Setting Theory of Electoral Competition Tiberiu Dragu and Xiaochen Fan

coverage or candidate discussion of certain policy issues induces citizens to give more weight to those issues when evaluating candidates (Ansolabehere and Iyengar 1994; Bartels 2006; Carsey 2000; Druckman et al. 2004; Iyengar and Kinder 1987; Jacobs and Shapiro 1994; Jacoby 2000; Johnston et al. 1992; Krosnick and Kinder 1990; McCombs and Shaw 1972), effects that have been shown both in observational and experimental studies. The model builds upon these well-documented empirical patterns to investigate the issue-selection strategies of candidates in electoral contests. Of course, not all voters are susceptible to agenda-setting effects. Specifically, some voters cast their votes on the basis of party identification regardless of the parties’ campaign messages. That is, such partisan voters have an allegiance for one party or another, and thus campaign messages and advertisements will have little effect on their voting decision. Notice that we could follow a similar modeling strategy as Baron (1994) and Grossman and Helpman (1996) and model the electorate as consisting of both a fraction of voters who are susceptible to campaign effects and a fraction of voters who are not; such modeling would not affect the forthcoming analysis, and thus we focus our model on those (nonpartisan) voters who can be susceptible to campaign effects. The game unfolds as follows. In the first stage, the parties simultaneously choose their advertising strategies regarding which issue dimensions to emphasize. The second stage is a standard voting game: each voter makes a decision regarding which party to elect.

PARTY COMPETITION AND ISSUE SELECTION In the voting stage, given the parties’ strategies of advertisement and the voters’ utility function as defined by expression (1), a voter with ideal policy x prefers party A over B if and only if n

n

o wi (a)(xi 2 pAi )2 ! ip o1wi (a)(xi 2 pBi )2 , ip1

The vote share of a party is the fraction of the electorate that prefers that respective party over the other party. For example, party A’s vote share is n

v (a , a ) p P x∣ o wi (a)(xi 2 pAi )2 ip1 ! n A

n

,

!

ð3Þ

!

ð4Þ

v (a , a ) p P x∣ o wi (a)di (xi ) 1 0 : ip1 A

A

B

Similarly, the vote share of party B is n

v B (aA , aB ) p P x∣ o wi (a)d i (xi ) ! 0 : ip1

Expressions (3) and (4) show that the vector d(x) ≡ fdi (xi )gnip1 is an important determinant of a party’s vote share; the parameter di(xi) is a measure of whether and by how much a voter with ideal policy x prefers party A over party B on issue i. Because the distribution of voters’ policy positions follows a multivariate normal distribution, the distribution of d(x) is also multivariate normal. That is, d(x) ∼ N(n A , L), where niA p (piA 2 pBi )½mi 2 ((piA 1 pBi )=2)$ is the 2 i-th element of vector n A and lii p (piA 2 pBi ) jii is the i-th diagonal entry of the variance-covariance matrix L.10 Similarly, we have nBi p (pBi 2piA )½mi 2((piA 1 pBi )=2)$ and therefore nBi ≡ 2niA . For simplicity of exposition, henceforth we use the notation ni p niA where indexing by party is not important and use the notation nki for k ∈ {A, B} where party indexing is necessary. Given that d(x) follows a normal distribution, we can rewrite party A’s and party B’s vote share as follows: v A (a A , aB ) p P(x∣w(a) ⋅ d(x) 1 0) 0

ð2Þ

where di (xi ) ≡ (pAi 2 pBi )(xi 2 (pAi 1 pBi )=2).9

o wi (a)(xi 2 pBi )2

ip1

which is equivalent to

n

o wi (a)di (xi ) 1 0,

B

!

which is equivalent to ip1

A

B p F@h

and

1

oip1wi (a)ni C i1=2 A, n oip1 wi (a)2 lii n

ð5Þ

v B (aA , aB ) p 1 2 v A (a A , aB ), 9. The first inequality is equivalent to

oip1 wi (a)(xi 2 pBi )2 2 oip1 wi (a)(xi 2 pAi )2 n p oip1 wi (a)ð pAi 2 pBi )(2xi 2 ( pAi 1 pBi )) n

p 2o

n

n

A ip1 wi (a)( pi

2

#

pBi )

pA 1 pBi xi 2 i 2

$

1 0,

which is equivalent to oip1 wi (a)d i (xi ) 1 0, where d i (xi ) ≡ (pAi 2 pBi )(xi 2 (pAi 1 pBi )=2). n

10. Since jij p 0 for all i ≠ j, we have lij p 0 for all i ≠ j. Therefore, the variance-covariance matrix L can be fully characterized by the diagonal entries lii p (pAi 2 pBi )2 jii .

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where F(⋅) is the cumulative distribution function of standard normal distribution.11 The parameters ni and lii are central to our analysis regarding the issue-selection strategies of parties. The parameter ni is a measure of party A’s electoral popularity on policy issue i. A positive ni implies that a majority of the voters prefers party A over party B on issue i; that is, party A has an advantage on issue i, and a higher value of ni implies a bigger electoral advantage for party A relative to party B on issue i. Conversely, a negative ni implies that a majority of the voters prefers party B over party A on policy issue i; that is, party B has electoral advantage on issue i, and a higher value of 2ni implies a bigger electoral advantage for party B relative to party A on policy issue i.12 How a party’s electoral popularity is aggregated across the n policy issues is determined by the salience of each issue dimension, wi (a). The parameter lii is a measure of electoral heterogeneity regarding which party is more desirable on issue i.13 A higher (lower) lii connotes a higher (lower) electoral heterogeneity regarding which party is more desirable on policy issue i. How the electoral heterogeneity is aggregated across the n issue dimensions is determined by the salience of each issue dimension, wi (a). Table 1 summarizes the relevant parameters in our subsequent analysis and their substantive interpretation. Given the parties’ vote shares previously described, party A’s optimization problem is 0 1

oip1 wi (a)ni C A A i1=2 A 2 C (a ): n 2 oip1 wi (a) lii n

B maxaA ∈Rn1 F@h

Note that the strategy space in our model is compact, even though we formulate the advertisement of each party as chosen from Rn1 . This is because

11. The calculation is as follows: v A (aA , aB ) p P(x∣w(a) ⋅ d(x) 1 0) # $ w(a) ⋅ d(x) 2 w(a) ⋅ n w(a) ⋅ n ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi pffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi p p P x∣ 1 2 p w0 (a)Lw(a) w0 (a)Lw(a) # $ # $ w(a) ⋅ n w(a) ⋅ n p F pffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi p 1 2 F 2 pffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi w0 (a)Lw(a) w0 (a)Lw(a) 0 1

oip1 wi (a)ni C i1=2 A: n oip1 wi (a)2 lii

B p F@h

n

12. Since mi is the center of xi, ni p (pAi 2 pBi )(mi 2 (pAi 1 pBi )=2) is the center of di(xi). 13. Since jii is the variance of xi, the parameter lii p (pAi 2 pBi )2 jii is the variance of d i (xi ) p (pAi 2 pBi )(xi 2 (pAi 1 pBi )=2).

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Table 1. Parameters in the Analysis Parameters

Substantive Interpretation

ni lii

oip1 wi (a)ni n

h

oip1 wi (a)2 lii n

i1=2

0

B F@h

Party A’s electoral popularity on issue i Electoral heterogeneity regarding which party is more desirable on issue i Party A’s electoral popularity on the n policy issues Electoral heterogeneity regarding which party is more desirable on the n issues

1

oip1 wi (a)ni C i1=2 A ≤ 1 n oip1 wi (a)2 lii n

for all aA , but C A (aA ) p oip1 cA (aAi ) and cA(∞) p ∞. Therefore, there exists aA 1 0 such that the above optimization problem is equivalent to maximizing the same objective A n function by choosing aA ∈ ½0, a $ . The same argument applies for party B’s optimization problem, which is defined as 2 0 13 6 B maxaB ∈Rn1 41 2 F@h

n

oip1 wi (a)ni C 7 B B i1=2 A5 2 C (a ): n 2 oip1 wi (a) lii n

In the spatial model of electoral competition, equilibria in pure strategy do not generally exist in a multidimensional policy space because the continuity condition necessary for the existence of such an equilibrium is satisfied only under very restrictive conditions. To overcome the continuity problem, scholars have developed probabilistic voting models (Coughlin 1992), where citizens vote according to probability functions based on their preferences and, as a result, equilibria in a multidimensional space exist provided that the parties’ utility functions satisfy a concavity condition which is typically assumed. Our set-up here is similar to probabilistic voting model as the continuity condition is satisfied in our framework because a party’s strategy is to choose an amount of advertisement on each issue and each party’s utility function is continuous in the advertisement strategies. Moreover, each party’s utility function is concave in its own strategy if the cost function is sufficiently convex.14 In the remainder of our analysis, we characterize the issue-selection incentives of parties in a pure strategy equilibrium. First, we show that the parties will not advertise the same policy issue. Intuitively, if both parties were to advertise 14. In the appendix, we show how one can impose conditions on the cost function to ensure that it is sufficiently convex so that a party’s utility is concave in its own strategy.

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some issue i in equilibrium, the optimization problems of parties imply that the vote shares of both parties increase in the advertisement on issue i. However, because increasing one party’s vote share implies decreasing the vote share of the other party, both parties’ objective functions cannot increase simultaneously in the advertisement on issue i. Thus we have the following result: Proposition 1. The two parties do not advertise the same policy issue in a pure strategy equilibrium (i.e., B% aA% i ai p 0 for all i p 1, 2, ::: , n). A policy issue in our framework can be interpreted both as a policy area such as national security or the economy, but also as a dimension within a policy area such as the unemployment or the deficit, both of which are economic issues. Proposition 1 does not exclude the fact that both parties can advertise the same policy area, but it suggests that even when parties do so, they will emphasize different considerations of that respective policy domain. For instance, both parties could emphasize the topic of law and order in an electoral campaign; however, proposition 1 suggests that they will raise the salience of different aspects. The 1992 presidential election offers an example: both parties talked about crime; however, the Republicans emphasized punishment, while the Democrats stressed prevention as the main way of tackling crime (Holian 2004). Before we proceed with analyzing the issue-selection strategies of parties, we present a simple example to illustrate the key mechanism that allows us to derive new theoretical results on the strategy of issue selection: increasing the salience of an issue affects a party’s vote share by changing the electoral heterogeneity regarding which party is more desirable. To this end, consider party A’s utility: 0

1

oip1 wi (a)ni C A A i1=2 A 2 C (a ): n 2 oip1 wi (a) lii

B U A (a) p F@h

n

Naturally, one would expect that party A will advertise those issues on which it has an electoral advantage; that is, party A will advertise issues with ni 1 0 because such advertisement increases its electoral popularity. Emphasizing issues on which it has electoral advantage is an important consideration of party A’s strategic calculus, but it is not the complete story. There is another channel by which advertising an issue can change party A’s equilibrium vote share: changing the salience of an issue also affects the electoral heterogeneity regarding which party is more desirable.

To illustrate this mechanism, suppose that the parties’ policy positions are p Ai p 1 and p Bi p 0 for all issues and the center of the voter preferences is mi p m p 1 for all issues. Recall that the electoral advantage of party A on issue i is ni p ( pAi 2 pBi )½mi 2 (( pAi 1 pBi )=2)$. Given our parametric specifications, we have ni p 1=2 for all issues, which implies that party A’s vote share is 0 1 1 B C F@ h n i1=2 A: 2 oip1 wi (a)2 lii

Notice that party A wins a majority of votes in this example since party A’s policy position is the same as the center of voter preferences on every issue, while party B’s policy position is to the left of the center of voter preferences on every issue. In this example, the electoral popularity of party A is the same regardless of which issues party A emphasizes. Since party A cannot affect its vote share by strategically selecting issues to increase its electoral popularity, party A will select which issue to advertise on the basis of lii (a similar reasoning holds for party B in this example). But how do parties select which issues to advertise to increase their vote share through the electoral heterogeneity channel? Recall that the electoral heterogeneity on issue i is lii p (pAi 2 pBi )2 jii . Given our parametric specifications, we have lii p jii for all i, which implies that party A’s vote share is 0 1 1 B C F@ h i1=2 A: n 2 oip1 wi (a)2 jii

In other words, in this example, parties can affect their vote share by selecting which issue to advertise on the basis of jii since a higher jii implies a higher electoral heterogeneity on issue i. To investigate whether a party prefers to spend a unit of advertisement on an issue with higher or an issue with lower electoral heterogeneity, consider a version of our example with two issues that differ only in the variance of voter preferences such that j22 1 j11. Figure 1 illustrates graphically this example: the distribution on the top represents the distribution of voter preferences on issue 1, and the distribution on the bottom represents the distribution of voter preferences on issue 2. Issue 1 depicts an electorate in which voter preferences are more concentrated, while issue 2 depicts an electorate in which voter preferences are more dispersed around the center of the electorate. As a result, the electoral heterogeneity regarding which party is more desirable is lower on issue 1 than on issue 2, that is, l11 ! l22.

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words, our characterization results hold for all equilibria regardless of whether party A or party B is the majority party after advertisement.15 The previous example isolates one mechanism by which issue advertisement affects a party’s vote share. In general, when a party chooses which issues to advertise, its issueselection strategy impacts the equilibrium vote share by simultaneously affecting both the electoral popularity of a party and the electoral heterogeneity regarding which party is more desirable. In the next sections, we show that how these two mechanisms, together with whether a party is the minority or the majority party, determine the equilibrium issue-selection strategy of a party.

ELECTORAL ADVANTAGE AND ISSUE SELECTION Figure 1. The effect of electoral heterogeneity on a party’s vote share

As mentioned, on either of the issues, party A wins a majority of votes; however, party A’s vote share is higher on issue 1 than on issue 2 because the strength of party A’s electoral support is higher when voter preferences are more homogeneous. On the other hand, party B’s vote share is higher on the issue on which voters’ policy positions are more dispersed because the majority support of party A on that issue is weaker. As a result, in a two-issue electoral competition, party A is better off if the distribution of the electorate on the two issues is more like issue 1, while party B is better off if the distribution of voter preferences on the two issues is more similar to that of issue 2. Consequently, if parties were to decide how to spend a unit of advertisement, party A prefers to advertise issue 1 rather than issue 2, whereas party B has the opposite incentives. Similar to this example, whether a party wins or not a majority of votes on the n issues after advertisement is an important determinant for understanding the issue-selection strategies of parties in our subsequent analysis. Henceforth, for simplicity of exposition, we label the party with the higher equilibrium vote share after advertisement as the majority party and the party with the lower equilibrium vote share as the minority party. That is, party k is the majority party if n oip1 wi (a∗ )nki 1 0. Of course, which of the two parties is the majority party in an electoral contest depends on the exogenous parameters (e.g., the distribution of voters’ ideal policies, the parties’ cost functions of issue advertisement). The identity of the majority party and minority party is not relevant for our results since we characterize the issue-selection incentives of parties in any pure strategy equilibrium. In other

In his influential analysis of the strategy of campaigns, Riker (1996) argues that a party does not advertise an issue on which neither of the two parties has advantage (the dispersion principle) or an issue on which the opponent has advantage (the dominance principle). The dispersion principle implies that neither of the parties advertises an issue with ni p 0 because such advertisement has no effect on a party’s electoral popularity but it is costly. The dominance principle implies that, for example, if party B advertises an issue on which party A has an electoral advantage (i.e., ni 1 0), such advertisement is detrimental because it increases the electoral popularity of party A. As mentioned, this reasoning captures only one of the effects of promoting an issue in that it ignores the fact that advertising an issue also affects a party’s vote share by changing the electoral heterogeneity regarding which party is more electorally desirable. For instance, if a party advertises an issue on which its opponent has electoral advantage, such advertisement indeed increases the opponent’s vote share by increasing its electoral popularity, but it also changes the opponent’s vote share by affecting the electoral heterogeneity regarding which party is more desirable. If the effect of such strategy on electoral heterogeneity is such that it increases the opponent’s vote share, then the two mechanisms work in the same direction. However, if advertising an issue on which the opponent has electoral advantage affects electoral hetero-

15. Notice that it is possible in our framework for the party with a higher vote share in the absence of advertisement to be the minority party after advertisement. Such a situation can happen if the cost of advertisement of the ex ante advantaged party is higher than the advertisement cost of its opponent. We characterize the properties of pure strategy equilibria in terms of the issue-selection strategies of parties and thus our analysis holds for all scenarios, including those in which the ex ante advantaged party is the minority party after advertisement.

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geneity in a manner that leads to a decrease in the opponent’s vote share, then the two mechanisms work in opposite directions. In this section, we show that the two mechanisms work in the same direction for the majority party but in opposite directions for the minority party. This implies that there can be situations in which the minority party finds it optimal to promote an issue on which it holds an unpopular position. By the same rationale, the minority party has incentives to advertise an issue on which neither of the party has electoral advantage. To show these incentives of the minority party consider first the case of a neutral issue. The next example shows that the minority party benefits electorally by advertising an issue with ni p 0. Example 1. Suppose that there are three issues, party A has electoral advantage on issue 1, party B has electoral advantage on issue 3, and neither party has advantage on issue 2. Let n1 p 10, n2 p 0, n3 p 22, l11 p 1, l22 p 100, l33 p 1, and the weight function be ! " ! " wi (a) p ai 1 1 = oi ai 1 3 . For simplicity, let the action space of each party be binary, aki ∈ f0, 1g and the cost of advertising an issue be c k(0) p 0 and c k (1) p 0.05 for k ∈ {A, B}. Given these specifications, there is an equilibrium in which party B advertises on issues 2 and 3 (i.e., aB p (0, 1, 1)) and party A advertises on issue 1 (i.e., aA p (1, 0, 0)). In this equilibrium, the weights of the three issues are equal, wi p pffiffiffiffiffiffiffi 1/3, the vote share of party A is F(8= 102) ≃ 0:79, and pffiffiffiffiffiffiffi the vote share of party B is 1 2 F(8= 102) ≃ 0:21. Party B is the minority party and advertises issue 2, on which neither party has an electoral advantage.

if the minority party’s support on that issue slips slightly below 50% so the majority party has a slight electoral advantage, the minority party would still have incentives to advertise it. Hence, the minority party may advertise an issue on which its opponent has electoral advantage. Example 2 illustrates such a scenario. Example 2. Suppose that there are three policy issues, party A has electoral advantage on issues 1 and 2 and party B has electoral advantage on issue 3. Let n1 p 10, n2 p 1, n3 p 22, l11 p 1, l22 p 100, l33 p ! " 1, and let the weight function be wi (a) p ai 1 1 = " ! oi ai 1 3 . For simplicity, let the action space of each party be binary, aki ∈ f0, 1g and the cost of advertising an issue be c k(0) p 0 and c k(1) p 0.05 for k ∈ {A, B}. Given these specifications, there is an equilibrium in which party B advertises on issues 2 and 3 (i.e., aB p (0, 1, 1)) and party A advertises on issue 1 (i.e., aA p (1, 0, 0)). In this equilibrium, the weights of the three issues are equal, wi p 1/3, the vote share pffiffiffiffiffiffiffi of party A is F(9= 102) ≃ 0:81, and the vote share of pffiffiffiffiffiffiffi party B is 1 2 F(9= 102) ≃ 0:19; thus party B is the minority party, and party A is the majority party. Party B does not have a profitable deviation to a2 p 0 because if party B were not to advertise issue 2, the weights on the three issues would be w1 p 2/5, w2 p 1/5, w3 p 2/5, party A’s vote share would be F(17= pffiffiffiffiffiffiffi 108) ≃ 0:95, and party B vote share would be 1 2 pffiffiffiffiffiffiffi F(17= 108) ≃ 0:05.

Proposition 2 shows that the minority party has strict incentives to advertise a neutral issue since promoting such an issue increases its vote share.16 Intuitively, by continuity,

The previous example is set up as minimally as possible to highlight the minority party’s incentives to advertise an issue on which the opponent has electoral advantage. In particular, we restrict the strategy of a party to a discrete choice of advertisement aki ∈ f0, 1g, which implies that party B cannot spend more than one unit of advertisement on any issue. One might conjecture that, if given the option, party B might find it beneficial, for example, to allocate the unit of advertisement spent on issue 2 to issue 3 instead. This might be the case because party B has advantage on issue 3 and because, having already spent a unit of advertisement on issue 3, issue advertisement is perhaps more effective the more focused it is. To show that party B’s incentives to advertise an issue on which its opponent has electoral advantage are robust to such considerations, let us analyze a modified version of example 2.

16. By the same logic, the minority party will advertise an issue on which it has an electoral advantage.

Example 3. All parameters are as in example 2 except that party B can allocate the 1 unit of advertisement spent on issue 2 on issue 3 instead and the extra

More generally, the minority party’s vote share increases in the advertisement of a neutral issue. Proposition 2 shows that the minority party advertises an issue on which neither party has electoral advantage in any pure strategy equilibrium. Proposition 2. The minority party always advertises an issue on which neither party has electoral advantage (i.e., if k is the minority party, then ak% i 1 0 for all i such that ni p 0 and lii 1 0).

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unit of advertisement spent on issue 3 would cost 0 but if party B spends it on advertising issue 2, the cost is 0.05. In this scenario, the allocation of advertisement are aB p (0, 0, 2) and aA p (1, 0, 0), and the weights are w1 p 2/6, w2 p 1/6, and w3 p 3/6. Party pffiffiffiffiffiffiffi A’s vote share is F(15= 113) ≃ 0:92 and party B’s pffiffiffiffiffiffiffi vote share is 1 2 F(15= 113) ≃ 0:08. Thus party B is worse off to allocate the (extra) unit of advertisement to issue 3 than to issue 2 even if it is costless to allocate the unit of advertisement on issue 3 on which party B has an electoral advantage. Example 3 shows that the result that a party may advertise an issue on which its opponent has electoral advantage does not depend on the relative cost of advertising an issue on which that respective party has electoral advantage versus an issue on which the opponent has electoral advantage. Spending a marginal unit of advertisement on an issue on which the opponent has electoral advantage is costly because of the increased electoral popularity of the opponent and because of the opportunity cost of such advertisement (which could be high or low, depending on the assumption on the cost function and what kinds of issues on which the minority party has electoral advantage are available). However, these costs are balanced against the benefits of changing the electoral heterogeneity regarding which party is more desirable, and such benefits depend on the magnitude of lii. Fixing the aforementioned costs, if lii is big enough, the minority party finds it beneficial to advertise an issue i on which the opponent has electoral advantage. Taken together, the previous examples and proposition 2 show that the minority party has incentives to advertise an issue on which its opponent has electoral advantage or an issue on which neither party has electoral advantage. On the other hand, the majority party will not advertise such issues in equilibrium when voters’ positions across issues are uncorrelated. By advertising, for example, an issue on which the minority party has electoral advantage, the majority party will decrease its electoral popularity and, at the same time, increase the electoral heterogeneity regarding which party is more desirable on the n issues. These effects are working in the same direction to decrease the majority party’s vote share. By a similar logic, the majority party will never advertise a neutral issue. We have the following result: Proposition 3. The majority party does not advertise an issue on which its opponent has electoral advantage or an issue on which neither party has electoral advantage (i.e., if party k is the majority party, then k ak% i p 0 for all i such that ni ≤ 0).

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IDEOLOGICAL HETEROGENEITY AND ISSUE SELECTION In this section, we assess the counterfactual of which issues a party is more likely to emphasize on its electoral agenda if that party were to decide between two issues that differ only in terms of electoral heterogeneity (lii 1 ljj and n ki p n kj ) or between two issues that differ only in terms of a party’s electoral advantage (n ki 1 n kj and lii p ljj). Whether a party is the majority or the minority party (i.e., a party’s equilibrium status) determines if a party emphasizes more an issue with higher or lower electoral heterogeneity. Suppose that party A is the majority party and consider its incentives to advertise issue i or issue j when lii 1 ljj and ni p nj. If party A were to advertise more issue i than issue j (a%i 1 a%j 1 0), party A would have a profitable deviation: it can switch the advertisements on issue i and j. Such a deviation will not change the relative salience of issues other than i and j, the cost of advertisement or party A’s electoral popularity (because ni p nj), but it decreases the electoral heterogeneity regarding which party is more desirable on the n issues because lii 1 ljj. Therefore such a deviation increases party A’s vote share, which implies that party A will not advertise more an issue with higher electoral heterogeneity. On the other hand, the minority party has the opposite incentives: to advertise the issue with higher electoral heterogeneity so as to increase the electoral heterogeneity regarding which party is more desirable on the n issues. Such a strategy increases the minority party’s vote share by decreasing the majority party’s advantage on the n issues. To show these different incentives consider the following example: Example 4. Suppose that there are four policy issues; party B has electoral advantage on issues 1 and 2, and party A has electoral advantage on issues 3 and 4. Let n1 p n2 p 21, n3 p n4 p 2, l11 p l33 p 1, l22 p l44 p ! " 10, and the weight function be wi (a) p ai 1 1 = " ! oi ai 1 4 . For simplicity, each party can choose among three different levels of advertising on each issue, aki ∈ f0, 1, 2g for k ∈ {A, B}. The costs of advertisement are c k(0) p 0, c k(1) p 0.01 and c k(2) p 0.05 for k ∈ {A, B}. Given these specifications, we have an equilibrium in which party B’s strategy is aB p (1, 2, 0, 0), while party A’s strategy is aA p (0, 0, 2, 1). In this equilibrium, party A is the majority party and party B is the minority party; party A advertises more the issue with lower electoral heterogeneity, while party B advertises more the issue with higher electoral heterogeneity. This example illustrates a more general result, which is stated in the following proposition:

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Proposition 4. For any k ∈ {A, B} and any i, j among the issues party k advertises, if lii 1 ljj and ni p nj, k% k% then ak% i ≤ aj if party k is the majority party and ai ≥ ak% j if party k is the minority party. Proposition 4 shows that, in any pure strategy equilibrium, the minority party prefers to advertise more issues with higher electoral heterogeneity while the majority party puts more emphasis on issues with lower electoral heterogeneity regarding which party is more desirable.17 Given that the electoral heterogeneity of an issue is a function of the variance of voter preferences on that issue (i.e., lii p (pAi 2 pBi )2 jii ), if we were to compare two policy issues i and j with jii 1 jjj we have the following result: Corollary 1. For any k ∈ {A, B} and any i, j among the issues party k advertises, if jii 1 jjj, party k prefers to advertise issue i if it is the minority party and prefers to advertise issue j if it is the majority party, all else equal. Corollary 1 follows from the fact that lii is increasing in jii and the results regarding the majority and minority parties’ equilibrium incentives as stated in proposition 4. It suggests that the majority party prefers to advertise consensual issues (i.e., issues on which voters are more ideologically homogeneous), while the minority party prefers to advertise controversial issues (i.e., issues on which voters are more ideologically heterogeneous). Proposition 4 characterizes the distribution of advertisement among the issues that a party advertises relative to other issues on that party’s electoral agenda; it does not compare the pattern of issue advertisement across parties. In other words, proposition 4 does not imply that the issues on the majority party’s electoral agenda are less ideologically heterogeneous than the issues on the minority party’s electoral agenda since it does not characterize the pattern of advertisement of one party relative to the other party. To illustrate this point consider the following example: Example 5. Suppose that there are three policy issues, party A has electoral advantage on issue 1 and party B has electoral advantage on issues 2 and 3. Let n1 p 3, n2 p n3 p 2 1, l11 p 3, l22 p 2, l33 p 1, and the ! " ! " weight function be wi (a) p ai 1 1 = oi ai 1 3 . For simplicity, each party can choose among three dif17. Proposition 4 does not depend on assuming that the cost of adn vertisement is C k (ak ) p oip1 ck (aki ); the same result obtains if we assume that the cost of advertisement is C k (ak ) p c k (oi aki ), for example.

ferent levels of advertising on each issue aki ∈ f0, 1, 2g for k ∈ {A, B}. The costs of advertisement are cA(0) p 0, cA(1) p 0.03, cA(2) p 0.08, c B(0) p 0, c B(1) p 0.05, c B(2) p 0.12. Given these specifications, we have an equilibrium in which party A’s strategy is aA p (2, 0, 0) while party B’s strategy is aB p (0, 2, 1). In this equilibrium, the majority party advertises issue 1 and the minority party advertises issue 2 and 3. Party B has the same electoral advantage on issue 2 and 3 but l22 1 l33 (i.e., the electoral heterogeneity is higher on issue 2 than on issue 3) so as suggested by proposition 4, party B advertises more issue 2. However, note that l11 1 l22 and l11 1 l33 in this example. Finally, we analyze the incentives of a party regarding which issue to advertise if that party were to choose between two issues that differ only in terms of their electoral advantage. Proposition 5 shows that both parties prefer to emphasize more the issue on which they have a bigger electoral advantage when choosing between two issues i and j such that nki 1 nkj and lii p ljj: Proposition 5. For any k ∈ {A, B} and i, j among the issues party k advertises, if nki 1 nkj and lii p ljj, then k% ak% i ≥ aj . The intuition for proposition 5 is simple: when the issues are not differentiated in terms of electoral heterogeneity regarding which party is more desirable (i.e., lii p ljj), both parties prefer to advertise the issue on which a party has a bigger electoral advantage since such an advertisement strategy increases the overall electoral popularity of the party. In the appendix, we also analyze the issue-selection incentives of parties in the case in which voter preferences across various issues are correlated to show that our results are robust to this extension.

CONCLUSION Scholars have extensively documented that parties compete by selectively emphasizing various issue dimensions to gain electoral advantage (Bèlanger and Meguid 2008; Budge and Farlie 1983; Druckman et al. 2009; Green and Hobolt 2008; Laver and Hunt 1992; Ward et al. 2015). In this article, we develop a multidimensional model of electoral competition to investigate how parties compete over which position issues to emphasize during electoral campaigns. The analysis uncovers a novel mechanism by which increasing the salience of a policy issue affects a party’s vote share, a mechanism that allows us to derive new theoretical results regarding what kinds of position issues a party is more likely to emphasize in electoral

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contests. We show that the minority party has incentives to advertise an issue on which the opponent has a more popular position or an issue on which neither party has electoral advantage. We also show that the minority party has incentives to emphasize on its electoral agenda issues on which the electorate is ideologically heterogeneous, whereas the majority party prefers to advertise issues on which the electorate is ideologically homogeneous. This article provides a foundation for moving toward a more complete understanding on the content of campaign communication in the context of positional issues. Our analysis proposes novel empirical predictions on how the structure of public opinion impacts the issue-selection strategy of candidates, which can foster further empirical research on electoral campaigns.18 First, it suggests that the minority party is more likely to advertise position issues on which the opponent is more popular. Second, our analysis suggests a certain pattern of advertisement: the minority party is more likely to campaign on more controversial issues (within the set of position issues on its electoral agenda), and the majority party is more likely to emphasize more consensual issues (within the set of position issues on its electoral agenda). Furthermore, the framework we developed in this article can be used to explore other questions pertaining to the strategy of issue selection in electoral contests. First, how the cost of advertisement affects electoral competition through issue selection is a promising next step. Scholars have shown that media bias or campaign financing can be consequential in electoral contests (DellaVigna and Kaplan 2007; Erikson and Palfrey 2000); a possible topic of further analysis is to delineate the conditions under which asymmetries in the cost of issue advertisement determine which party wins the electoral contest. Relatedly, technological changes in media landscape unquestionably affect the cost of issue advertisement; another topic of future research is to investigate how changes in the structure of advertisement costs impact the number of issues that parties emphasize during electoral campaigns. Second, when a party controls the government, that party might have a first mover advantage regarding which issues to put forward on the public agenda. In other words, the incumbent party can take certain actions while governing to raise the electoral salience of certain issues; for example, a military intervention raise the salience of security issues. Study-

18. Recent statistical developments in applying automated content methods to political language can make possible the systematic analysis of large-scale text collections to identify, for example, how much emphasis a candidate places on a certain policy issue (for an overview of automated content methods and their application to political texts, see Grimmer and Stewart [2013] and Laver, Benoit, and Garry [2003\).

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ing the dynamics of issue advertisement in a framework in which one party has the first mover advantage is another promising extension of our framework.

ACKNOWLEDGMENTS We thank Alessandra Cassela, Torun Dewan, Daniel Diermeier, Patrick Egan, Georgy Egorov, Jean Guillaume Forand, Justin Fox, Sean Gailmard, Niall Hughes, Sanford Gordon, Navin Kartik, Dimitri Landa, Michael Laver, Alessandro Lizzeri, Massimo Morelli, Mattias Polborn, Robert Powell, Michael Ting, Bruno Strulovici, Antoine Yoshinaka, seminar participants at Columbia University, London School of Economics and Political Sciences, New York University, Stony Brook University Workshop on Political Economy, Toronto Political Behavior Workshop, University of California, Berkeley, and three anonymous reviewers for helpful comments and suggestions. All errors are ours.

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