This book explores the process of popular mobilization in contemporary Mexico through the experience of the country's most important organization--the teachers' movement. It creates a distinctive perspective on Mexican politics and makes an original contribution to the study of popular, or "social" movements, providing a richly detailed account of its organization, leadership, strategic choices, and factional divisions. But it also links the trajectory of the movement to the shifting legal and institutional terrain that composes its political environment, so revealing how it is shaped by, and how it shapes the political system. Through its innovative methods, which produce an unusual and compelling blend of fact and theory, the book uncovers the motivations and mechanisms of popular mobilization, as well as explaining its interactions with national politics in Mexico and beyond.