Ideological externalities, social pressures, and political parties

Amihai Glazer 0 0 A. Glazer ( ) Department of Economics, University of California , Irvine, CA 92697, USA Members of political parties may influence each other. For example, a liberal in a party of moderates may moderate his views. At the same time, the moderates in the party may become more liberal. Voters in a district who favor such effects may care about the ideology of officeholders in other districts. They may therefore prefer a candidate who affiliates with a party over an independent with the same position. Notation Mj Membership of party j n Number of districts other than the one under consideration Vi Ideal point of voter in district i Vj0 Initial ideology of candidate from district j Vj1 Induced ideology of the MC from district j w Weight in voter's utility function reflecting externality from MC's ideologies in other districts. Weight affecting MC's induced ideal point This paper uses ideas from social networks to explain why voters may prefer a candidate who joins some political party over an otherwise identical candidate who joins a different party or no party. It considers a political party as a social organization, with its members influencing each other. A voter may dislike having the district's representative swayed by the views of other party members. But a voter may want representatives from other districts I am grateful to a referee and to the associate editor for comments which allowed me to improve the paper. - to move closer to the voters ideology. The balance of these two opposing effects can make a voter prefer a representative who joins a party. The paper makes several contributions. First, it shows how a candidate can win votes by joining a party. Second, the analysis has membership in parties endogenousa candidate will join the party that maximizes his popularity within his constituency. Third, it allows the parties to form endogenously. In particular, rather than taking the ideology of parties as given, the paper shows that in equilibrium two parties may form, one on the left and one on the right. Fourth, following Krehbiel (1993), the analysis allows a political party to influence behavior, rather than merely to agglomerate like-minded officials. Of course, many other papers, including those surveyed below, consider the electoral benefits of political parties. Some, but not all, of these explanations satisfy an important criterion formulated by Krehbiel (1993). He notes that legislators who share preferences or other motivating factors will naturally show voting patterns that appear consistent with party behavior, independent of the partys existence. Thus, it is important to distinguish partylike behavior from changes in behavior caused by parties. My approach does this. 2 Literature Others have studied the electoral benefits to a candidate of joining a political party. One approach emphasizes that a political party can commit to future policy.1 Others see parties as long-run players that discipline candidates with short horizons. Alesina and Spear (1988) model a political party as an infinite sequence of overlapping generations of finitely-lived politicians; they describe a transfer scheme between a candidate and the party which allows a partys current and future candidates to commit to a moderate platform and thereby to increase electoral success. Harrington (1992) demonstrates how explicit commitment is unnecessary: a trigger strategy can allow parties to sustain moderate platforms. The benefits of party formation in a legislative bargaining game are modeled by Jackson and Moselle (2002): if legislators propose policies in random order, then legislators who bind themselves to make proposals that benefit each other will enjoy higher expected utility than when each acts independently. A different approach emphasizes how party membership informs voters. Thus, Snyder and Ting (2002) view a candidate as inclined to join a party with members whose positions are similar to his. Party membership then informs voters of the candidates positions, and therefore with risk-averse voters increases his electoral popularity. Caillaud and Tirole (2002) interpret parties as information intermediaries that select high-quality candidates. 2.1 Peer-group effects Experimental evidence shows strong social influences on individual judgment (e.g., Sherif 1935; Festinger et al. 1950; and Asch 1951). A fine survey of this literature is Marsden and Friedkin (1993). Data also show the existence of social influences on the behavior of politicians. Fenno (1978) speaks of a legislators personal constituency, which includes fellow legislators, as influencing him. Several authors examine friendship among legislators, finding that a legislator is especially likely to befriend legislators of the same party, and that friends are more likely to vote the same way on roll-calls. In a study of 93 members of the 1For example, Levy (2000) and Baron (1993) assume parties are constrained in their platforms, thereby increasing their power when they bargain over forming a coalition. Ohio State Legislature in 1993, Arnold et al. (2000) find that friendship increased shared voting, even after controlling for party and shared ideology.2 In the early 19th century, fraternities of congressmen nested in boardinghouses functioned as voting blocs; patterns of roll-call voting reflected the social networks derived from congressmens social lives (Young 1966). In the four legislatures Wahlke et al. (1962) study, members sought friendships within their own parties. And legislators who chose each other as friends tended to agree on roll calls. In the California Assembly, legislators who happen to be assigned seats next to each other tend to vote alike (Masket 2008). In the Iowa legislature, shared partisanship increases friendship (Caldeira and Patterson 1987). More generally, a persons beliefs can depend on the beliefs of others (Kuran 1995), and preferences may be endogenous (Becker and Murphy 1988). Friedkin (2003) formulates a social networks model of mutual influences, and describes experimental evidence supporting it. The ideas are applied to politics by Shleifer and Murphy (2004), who consider networks with mutual influences among their members. Like them, I find that in equilibrium political platforms can diverge, but unlike them I show how an individual politician benefits from joining a party. Aldrich (1983a, 1983b) sees party activists as concerned about the ideological stance of the party, and supposes that voters who find that the location of one partys activists are closer to their own preferences than that of the other party may become activists themselves. That in turn moves the location of the average party member in the direction of the new activist, which further affects who will join the party. The aggregation of the decisions of party activists may thus generate stable equilibria in which the two parties have different ideologies. My model also examines endoge (...truncated)