Traditional theories about government formation in parliamentary democracies are based on the assumption that parties can be characterized as unitary actors. Many authors have questioned the soundness of this assumption. The problem with keeping this assumption is that we may miss some important factors that explain why certain coalitions form if we do not consider the role of intraparty politics. In this paper, I evaluate two hypotheses drawn from a discussion about intraparty politics and coalition formation, which say that that internally democratic parties and factionalized parties are less likely to get into government. Using two different types of methods for evaluating coalition theories, on data from Swedish local government, I find support for both of these hypotheses. Thus, the conclusion is that we should consider the internal workings of parties when explaining and predicting coalition formation.
