Coalitions under Bicameral Presidentialisms: How the Upper Chamber Affects the Withholding of a Majority for the Government?

Bicameralism constitutes one of the most important differences between parliamentary and presidential systems. This supposes therefore a two-round procedure in the policymaking process for the president, increasing then the shadow of the unexpected. Indeed, controlling one of the two chambers may not be sufficient for the president so as to guarantee the approval of policies. The question is then to know what if a government doesn’t control both houses. In this case how do they proceed on the approval of policies? Finally, how coalition cabinets are affected by the uncontrolling of one chamber, if not both? We will focus our analysis on 16 governments of 4 south American countries (Argentina, Brazil, Chile and Uruguay) since the return of democracy. We will show therefore that presidential pro-active and reactive powers are not sufficient variables for the determination of presidential behaviour facing a minority in one of the two chambers.