The Impact of Electoral Rules on Legislative Parties: Lessons from the Brazilian Senate and Chamber of Deputies

In this paper, I reexamine the impact of electoral institutions on legislative party organization. A long-running theme in comparative politics is that Brazil's political party system is weakened by the structure of its electoral institutions. I revisit this research by comparing legislative parties in the Brazilian Chamber of Deputies with those in the Brazilian Senate. This comparison allows me to control for political history, constituents, and even the legislative agenda, while providing variance on the key explanatory variable—the electoral system. The Senate is very similar to the Chamber of Deputies, but does not use the much maligned open-list proportional representation (OLPR) rules. The result is a powerful opportunity for testing and inference. The comparisons reveal no consistent or significant differences between institutions.