Divergence in the Spatial Stochastic Model of Voting

Abstract

Much research has been devoted over the last few decades in an attempt at constructing formal models of political choice in electoral systems based on proportional representation (PR). In large degree these models have been most successful in studying the post-election phase of coalition bargaining (Laver and Schofield 1990; Laver and Shepsle 1996; Banks and Duggan 2000). Such models can take the locations and strengths of the parties as given. Attempts at modelling the electoral phase have met with limited success, since they have usually assumed that the policy space is restricted to one dimension, or that there are at most two parties. The extensive formal literature on two party electoral competition was typically based on the assumption that parties or candidates adopted positions in order to win (Calvert 1985.) In PR systems it is unlikely that a single party can gain enough votes to win outright (Cox 1990, 1997; Strom 1990).