On the role of the primary system in candidate selection

Abstract

How does the type of the primary system affect political outcomes? We address this issue by constructing a simple model that accounts for intra-party as well as inter-party political competition. Our model suggests that allowing non-partisan voters to participate in the primaries (i.e. a semi-open primary system) indeed improves the chances of a moderate candidate getting elected. However, this need not necessarily happen in the case of a completely open primary system. Under such a system there arise multiple equilibria, some of which may lead to a greater degree of extremism than the closed primary system. Thus, our model contributes to the current debate on the choice of primary systems from an analytical perspective and helps explain some of the empirical findings.