Activist Coalitions: Modeling Elections and Regime Change

之前由提议的PI（在NSF资助下SES 024173）与许多合作者一起进行的实证研究已经为英国、以色列、意大利、荷兰和美国开发了随机选举模型。这项研究表明，向选举中心的趋同（通常由选举模型预测）是非常不可能的。为了解释非收敛性，建立了一个基于外生价的正式模型。一个政党的领导人或候选人的价值是由选民根据其过去的表现或预期的未来表现对其素质的平均评价决定的。这一理论证明了存在收敛性的充分必要条件。如果各方之间的价电子差足够大（在经验模型参数给出的精确意义上），低价电子将不得不采取激进的立场。这一理论解释了戈德华特在1964年美国大选中的立场，以及以色列在1988年、1992年和1996年选举中政党立场的分歧。然而，英国、意大利和荷兰选举的经验模型表明，这些选举中的价格差异不足以解释观察到的差异。这些结果表明，一个更好的选举模式应该包括活动家对候选人立场的影响。这样一个模型将提供一个更复杂的解释，说明政党在回应激进分子影响时的定位。目前的建议是基于存在两种价的假设，发展和应用一种一般的随机选举模型。第一类是固定价或外生价（如在较早的模型中），它被认为与政党立场无关。然而，由于活动人士为他们选择的政党提供了重要的时间和金钱资源，政党可以利用这些资源在选民面前提升自己的形象，从而影响其整体价值。在本文提出的模型中，使用“积极价”一词来表示积极资源的影响。这些可以通过媒体等间接影响选民，使选民更有可能支持政党。两党面临的问题是，激进分子往往比普通选民更为极端。通过选择政策立场来最大化活动家的支持，该党将失去中间派选民。因此，政党必须计算出使选票份额最大化的最佳边际条件，或者其他一些最大值，例如选举成功的概率。作为提出的研究基础的理论结果是一个（一阶）平衡条件，它封装了这种权衡的逻辑。此外，由于积极分子的支持是以时间和金钱来衡量的，因此可以假设积极分子的函数将表现出递减的回报，从而导致各方采取最优立场的纳什均衡的存在。这些纳什均衡将取决于激进组织为他们选择的候选人提供资源的意愿。这种模式隐含着在移民、堕胎、支持干细胞研究等领域的政策上，激进分子发生冲突的可能性。

Previous empirical research by the proposed PI (under NSF Grant SES 024173), together with a number of collaborators, has developed stochastic electoral models for Britain, Israel, Italy, the Netherlands and the United States. The work suggests that convergence to an electoral center (often predicted by electoral models) is very unlikely. In an attempt to explain non-convergence, a formal model based on exogenous valence was developed. The valence of a party leader or candidate is determined by the average evaluation by the electorate of the quality of the leader, based on past performance, or expected future performance. This theory showed that there were necessary and sufficient conditions for convergence. If the valence difference between the parties was sufficiently high (in a precise sense given by the parameters of the empirical model), the low valence parties would be obliged to adopt radical positions. The theory explained the position of Goldwater in the 1964 US election, as well as divergence of party positions in Israel in the elections of 1988, 1992 and 1996. However, the empirical models of elections in Britain, Italy and the Netherlands indicated that the valence differences in these elections were insufficient to explain the observed divergence. These results suggested that a superior electoral model should incorporate the influence of activists on candidate positions. Such a model would provide a more sophisticated account of party positioning in response to activist influence. The current proposal involves the development and application of a general stochastic model of elections based on the assumption that there are two kinds of valence. The first kind is the fixed or exogenous valence which (as in the earlier model) is assumed to be independent of party position. However, since activists provide crucial resources of time and money to their chosen party, the party can use these resources to enhance its image before the electorate, thus affecting its overall valence. In the model presented in the current proposal, the term activist valence is used to denote the effect of activist resources. These can indirectly influence voters, through the media etc., so that voters become more likely to support the party. The problem for each party is that activists tend to be more extreme than the typical voter. By choosing a policy position to maximize activist support, the party will lose centrist voters. The party must therefore calculate the optimal marginal condition to maximize vote share, or some other maximand such as probability of electoral success. The theoretical result used as the basis for the proposed research is a (first order) balance condition which encapsulates the logic of this trade off. Moreover, because activist support is denominated in terms of time and money, it can be assumed that the activist functions will exhibit decreasing returns, leading to existence of a Nash equilibrium where parties adopt optimal positions. These Nash equilibria will then depend on the willingness of activist groups to provide resources for their chosen candidates. Implicit in this model is the possibility of activist conflict over the policies in areas such as immigration, abortion, and support for stem cell research.