We study a model of party formation in which party discipline and inter-party ideological heterogeneity are endogenously and jointly determined. Discipline benefits party members because it gives risk-averse voters more confidence in the ideological composition of the party, but this discipline is costly to members who win office. Equilibrium is determined by balancing these forces. We show that this model can account for both comparative difference between parliamentary and presidential systems, and changes over time in the U.S. Congress.

We analyze a model of constituency service provision to understand how the level of constituency service responds to variation in both institutions and the competitiveness of elections. We show that single-member districts, separately elected executives, and more ideologically balanced electorates all increase incentives for constituency service. We use these results to explain why constituency service and party strength are negatively related in comparative evidence but positively related in historical evidence. We also discuss incentives for divided delegations and for personalized constituencies in multi-member districts.