Theories of institutional development have tended to view discretion, or the leeway to act within institutional bounds, as an often unintended consequence of agency design and institutional specification. Yet the post-communist states show that discretion is a fundamental goal of institutional creation among competing elites. In turn, while political competition has been identified as a key constraint on discretion in institutional creation, widely-used indicators of political competition are inadequate. As post-communist democracies show, the number or seat share of political parties matters far less than what parties do in parliament. The key factor is a robust opposition: a clear, credible, and contentious threat to governing parties. Such opposition leads to the rise of formal institutions that both minimize the discretion necessary for rent-seeking, and favor equitable distributional outcomes.