A spatial model of political competition and proportional representation

Abstract

A spatial model of party competition is studied in which: (i) Parties are supposed to have ideology. By this we mean that their goal is to maximize the welfare of their constituencies. (ii) The policy implemented after the election does not need to coincide with the one proposed by the winner. The policy implemented should be a compromise that considers the proposals made by the di¤erent parties. In the case of proportional representation this compromise is modeled as a convex combination of the proposed policies with weights proportional to the number of votes obtained by each party. We provide some existence theorems and compare the equilibrium in our model with the equilibrium that exists under some probabilistic models. It is also shown that proportional representation will create incentives for the parties to announce radical platforms.