The higher legislative success of parliamentary governments relative to presidential governments has been used to argue that legislative success is driven by parliamentary governments' superior agenda power or their control of legislative majorities. We show that this approach is at odds with some of the empirical regularities across and within political systems. We then propose a legislative bargaining model to elucidate this puzzle. In the model, the policies of a confidence-dependent parliamentary government enjoy more predictable support from governing coalition members because their short-term policy goals are less important than the government's survival. Coalition support is stronger when the government has more agenda power and is weaker with a larger ruling coalition. We explore the empirical implications of these findings and their consequences for the comparative study of legislative institutions.

This paper presents a theory of parliamentary systems with a proportional representation electoral system, a formateur selected based on party representation in parliament, and parties that cannot commit to the policies they will implement once in government. Government formation involves efficient proto-coalition bargaining, and elections yield unique strong Nash equilibrium outcomes. Depending on the status quo, minimal-majority, surplus, or consensus governments can form. If parties and voters are myopic and the status quo is subject to shocks, consensus governments and centrist policies occur only in a crisis. Otherwise, governments are minimal winning, and policies reflect only the preferences of the government parties.