Special interest groups and election outcomes

Election outcomes over the last decade in the Netherlands have been quite volatile. Identification of voters with special interests, such as immigration or the 'hypotheekrenteaftrek', might play an important role in explaining this phenomenon. In this short paper we consider a spatial model of electoral competition between two political parties. We show that, by coordinating voting behavior, identification with interest groups may increase the winning set, which is the set of policy platforms for the challenger that defeat the incumbent. Therefore identification with interest groups may enhance the likelihood the challenger wins the election. This leads to more unstable election outcomes. A simulation study confirms these conjectures.