Endogenous Parties in an Assembly . The Formation of Two Polarized Voting Blocs . ∗ Jon

In this paper I show howmembers of an assembly form voting blocs strategically to coordinate their votes and affect the policy outcome chosen by the assembly. In a repeated voting game, permanent voting blocs form in equilibrium. These permanent voting blocs act as endogenous political parties that exercise party discipline. In a stylized assembly I prove that the equilibrium parties must be two small polarized voting blocs. In an empirical application of the model to the US Supreme Court, I again predict that the equilibrium outcome of strategic coalition formation in the Court would lead to the formation of two voting blocs, one at each side of the ideological divide.