Why do new democracies succeed in some cases and struggle, backslide, or revert entirely to autocracy in others? What are the specific policies and practices at play? To answer these questions, Benjamin Cole turns to James Madison’s “mischief of faction,” drawing on a broad array of detailed case studies to demonstrate that factionalism is the most powerful predictor of adverse regime change and state failure in emerging democracies—and an existential threat to mature democracies, including the United States.