Collaborative Research: An Informational Rationale for Political Parties

政党在选举竞争中扮演什么角色？ 为什么政党要对党员实行纪律？ 本研究通过将政党作为选民的信息品牌，将这些问题从理论和经验上联系起来。正如传统智慧所表明的那样，大多数政党标签都有相当精确的含义。民主党人通常是自由主义者，共和党人通常是保守主义者，而自由意志主义者基本上是保守主义者，但往往是社会自由主义者。理论上的问题是，这是如何作为一个均衡现象持续下去的？ 在基本模型中，研究人员假设有大量的选区，选民是风险厌恶和不完全了解候选人的理想政策，候选人无法承诺宣布的政策平台。在这种环境下，政党可以通过聚集意识形态相似的候选人来发挥关键作用。重要的是，党员身份是内生的。因此，不同类型的候选人有动机加入一个政党，以减少选民对他们偏好的不确定性。(1)政党可以成为筛选候选人偏好的有效工具。直觉上，这种筛选之所以有效，是因为政党成员身份对不同意识形态类型的候选人施加了不同的成本，因此只有那些偏好与政党平台非常接近的候选人才愿意加入。 即使在一党制中，选民福利也会因政党候选人相对于无党派候选人能够传达的信息而增加。 (2)在两党制中，筛选的有效性和平台选择之间存在直接联系。 当加入各方的成本很高时，例如，政党可以有效地约束他们的成员或筛选出某些类型的候选人--政党标签信息量很大，政党的政纲以唐氏风格趋同。 然而，当政党标签信息量不足时，政纲就会出现分歧，因为采取极端立场会减少政党意识形态的异质性，从而使其标签对选民更有意义。 (3)候选人并不总是与最近的政党结盟，因为他们也考虑到了作为政党成员的选举利益。 这些福利可能因选民的偏好而异。 因此，即使是具有相同理想政策的候选人也可能加入不同的政党，这取决于他们选区中间选民的偏好。基本模型的扩展提供了额外的预测。特别令人感兴趣的是，在激烈的竞选中，选民对候选人的了解比我们在基本模型中假设的要多得多。 这种扩展可以解释政党标签有时在不同地方意味着不同的事情。 另一个延伸是将政党塑造成民主机构，这些机构必须集体选择平台和筛选机制，也许是通过初选制度。这包括政党数量的内生化，探索替代选举制度，以及确定筛选或纪律的最佳水平。初步结果和拟议的扩展都经得起实证分析。 我们将探讨的主题包括政党品牌的有效性、政党筛选和平台选择之间的关系、退休和叛逃模式以及平台随时间的演变。

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.