Effective parties in a model of repeated legislative bargaining

A self-enforcing, equilibrium account of legislative party organization in the context of the standard legislative bargaining model demonstrates how a members of a party could overcome the temptations to violate a party’s agreement to stick together on legislative matters in the absence of external enforcement. The model is robust, and realistic, in the sense that departures from the equilibrium path lead eventually to re-establishment of intra-party cooperation. Thus we construe legislative politics in a way that could support either a purely preference-based equi-librium or an equilibrium in which the legislature has an internal system of party organization that influences members sometimes to vote differently than they would based on their myopic issue preferences alone. There are multiple party equilibria of this type, and different ones would bring about wholly different outcomes. Hence party has a real effect beyond preference in determining legislative behavior