Collaborative Research: An Informational Rationale for Political Parties

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What role do parties play in electoral competition? Why would parties exert discipline on theirmembers? This investigation links these issues theoretically and empirically by modeling parties asinformative brands to voters.As conventional wisdom suggests, most party labels carry fairly precise meanings. Democratsare generally liberal, Republicans are generally conservative, and Libertarians are basically conserva-tive but often socially liberal. The theoretical question is, how is this sustained as an equilibriumphenomenon? In the basic model, the researchers assume there are a large number of constituencies, voters are risk averse and incompletely informed about candidate ideal policies, and candidates are unable tocommit to a declared policy platform. In this environment, parties can play a critical role by ag-gregating ideologically similar candidates. Importantly, party membership is endogenous. Certaintypes of candidates thereby have an incentive to affiliate themselves with a party to reduce voteruncertainty about their preferences.The results of a pilot by the investigators are the following. (1) Parties can be effective screening devices for candidate preferences. Intuitively, this screening works because party membership imposes differentialcosts across candidate ideological types, so that only candidates whose preferences are sufficientlyclose to a party 's platform are willing to affiliate. Even in a single party system, voter welfareis increased by the information party candidates are able to convey relative to unaffiliated candi-dates. (2) In a two party system there is a direct link between the effectiveness of screening andplatform choices. When the costs of joining parties is high-e.g., parties can effectively disciplinetheir members or screen out certain type of candidates -party labels are very informative, and theparties' platforms converge in Downsian fashion. When party labels are less informative, however,the platforms diverge.This happens because taking an extreme position reduces a party's ideolog-ical heterogeneity, thus making its label more meaningful to voters. (3) Candidates do not alwaysaffiliate with the nearest party, since they also take the electoral benefits of party membership intoaccount. These benefits may vary depending on constituency preferences. Thus even candidateswith the same ideal policy may affiliate with different parties, depending on the preferences of theirdistrict's median voter.Extensions of the basic model provide additional predictions. Of particular interest is thepossibility of hot races in which voters learn much more about candidates than we assume in ourbasic model. This extension can account for the fact that party labels sometimes mean differentthings in different places. Another extension is to model parties as democratic institutions that mustchoose platforms and screening mechanisms collectively, perhaps through a primary system. Othersinclude endogenizing the number of parties, exploring alternate electoral systems, and determiningthe optimal level of screening or discipline.Both the initial results and the proposed extensions are amenable to empirical analysis. Amongthe topics we will pursue are the effectiveness of party branding, the relationship between partyscreening and platform choices, retirement and defection patterns, and the evolution of platformsover time.