Why do people run for office with opposition parties in electoral authoritarian regimes, where the risks of running are high, and the chances of victory are bleak? In Activist Origins of Political Ambition, Keith Weghorst offers a theory that candidacy decisions are set in motion in early life events and that civic activism experiences and careers in civil society organizations funnel aspirants towards opposition candidacy in electoral authoritarian regimes. The book also adapts existing explanations of candidacy decisions derived from leading democracies that can be applied to electoral authoritarian contexts. The mixed-methods research design features an in-depth study of Tanzania using original survey data, sequence methods, archival research, and qualitative data combined with an analysis of legislators across authoritarian and democratic regimes in Africa. A first-of-its kind study, the book's account of the origins of candidacy motivations offers contributions to its study in autocracies, as well as in leading democracies and the United States.