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.