What Do Parties Do in Congress? Explaining the Allocation of Legislative Specialization

This article studies the determinants of the concentration of legislative specialization of parties across policy jurisdictions. Greater concentration of legislative specialization leads parties to concentrate their legislative efforts on a smaller set of policy jurisdictions. Through enhancing their concentration of legislative specialization in certain policy areas, parties can more clearly signal their policy concerns and interests to voters. This study argues and shows that relatively low electoral volatility and a low number of political parties (institutional traits) boost the concentration of legislative specialization. Greater electoral stability increases the incentives for parties to specialize further on certain policy jurisdictions. I also argue and verify that lower legislative fragmentation, producing larger parties, reduces the opportunity costs of legislative specialization. As I explain below, understanding the configuration of legislative specialization might help illuminate the evolution of key characteristics of party systems such as its degree of programmaticness and its degree of institutionalization, and to which extent parties are able to construct issue ownership.