The authors’ empirical analysis shows both commonalities and variations in the sources of regime support in Southeast Asian countries. Most regimes in the region draw political legitimacy from perceptions that their governance is effective and marked by integrity. These findings lend support to the argument that regime legitimacy—when it is won and when it is lost—is rooted in the output side of the political system. Yet delivering economic prosperity alone will not suffice. In order for political regimes in Southeast Asia to win over their people, they must control corruption, respect the rule of law, treat all citizens fairly and equally, expand public services, and be responsive to what the people need. The region’s young democracies are not exempt from these requirements.