Institute for Mathematical Behavioral Sciences

In this paper I study the strategic implications of coalition formation in an assembly. A coalition forms a voting bloc to coordinate the voting behavior of its members, acting as a single player and affecting the policy outcome. I prove that there exist stable endogenous voting bloc structures, and in an assembly with two parties I show how the incentives to join a bloc depend on the types of the agents, the sizes of the parties, and the rules the blocs use to aggregate preferences. I also provide an empirical application of the model to the US Supreme Court and I show that justices face a strategic incentive to coalesce into voting blocs.