Chapter 1 introduces how and why citizens often play a crucial role in the survival of clientelism.The persistence of clientelism across the world presents an intriguing puzzle, given the wide range of challenges that ostensibly threaten its existence.The chapter summarizes the book’s argument that vulnerability often spurs citizens to undertake actions that help sustain “relational clientelism” – ongoing exchange relationships with politicians who render assistance when adversity strikes.It introduces two key mechanisms – declared support and requesting benefits – by which citizens fortify these long-term clientelist relationships. The chapter distinguishes relational clientelism from electoral clientelism and other forms of distributive politics, and examines why the phenomenon is especially prone to opportunistic defection.It provides an overview of each chapter, and discusses scope conditions and broader implications.The chapter explains why Brazil presents a fortuitous context to test the argument; corroborative evidence is also provided from Argentina and Mexico, as well as from Ghana, India, Lebanon, Yemen, and cross-national surveys in Africa and Latin America.