Upton Sinclair's End Poverty in California campaign was international news in 1934. The socialist author was running for governor as a Democrat and pledging to enact an audacious plan to rebuild the state's economy through a “production for use” system of cooperative farms and factories. Tens of thousands joined his EPIC movement as he swept to victory in the primary and then watched in disbelief as he lost the general election. This article looks at the composition and dynamics of the EPIC movement, using new data to understand the class, ethnic, and gender profiles of activists and supporters. It attends closely to the geography of political institutions and political opportunity, showing why the movement appealed strongly to working-class voters in Los Angeles and how, in that setting, it attracted the talents of activists who were not usually drawn to left-wing politics.