3 Switching

Models of elections typically indicate that all parties, in equilibrium, will adopt positions at the electoral center. This situation, however, is seldom observed. This chapter outlines how an integrated theory of party strategy may be constructed based on a theorem for existence of Local Nash Equilibrium (LNE) in a stochastic electoral model where political agents have differing valence, or electorally perceived quality. In a model based on exogenous valence, it is shown that, under proportional representation, a high valence political leader may be motivated to switch party so as to control a centrist policy position. Under plurality rule, political agents may be forced to switch party as a result of the conflicting demands of activist coalitions. 3.1 A Model of Electoral Competition and Party Switching A fully developed formal theory of politics would connect the nature of the electoral system, the motivations of parties concerning policy and perquisites, and the process of government formation, in a way which makes sense of the empirical phenomena. A number of attempts have been made to model the motivations of parties in a game-theoretic framework. For example, one class of models is based on the Downsian framework, where parties compete via policy declarations to the electorate to maximize the number of seats they obtain. Since parties are assumed in these models to be indifferent to policy objectives, viewing policy solely as a means to gain power, symmetry would suggest that one equilibrium would be the situation where all parties declare the same position. In the standard spatial model Hellerm_Ch03.indd 55 3/6/2009 7:48:03 PM