This article seeks to answer an important puzzle in Brazilian politics: What explains the legislative struggles and defeats by a president who holds a large congressional base? In the post-democratization period, most Brazilian presidents have amassed large congressional bases of support by forming governing coalitions comprised of various legislative parties. Conventional wisdom would indicate that large legislative bases would facilitate presidents to pursue their legislative agenda. However, successive presidents have faced legislative obstruction, gridlock, and defeats in Congress. This article shows how Brazil’s political institutions engender the perpetual need for presidents to create multiparty coalitions to navigate through the system and how this impacts policymaking processes and political accountability. Specifically, (1) legislative coalitions have unique challenges that are not present in parties; (2) intra-coalition dynamics is at least as important as inter-coalition conflict in a coalitional presidential system; (3) failure to effectively manage coalitions generate greater legislative obstructionism and delay; and (4) challenges of managing coalitions have led to a series of accountability problems in Brazil.