This volume explains why some contemporary Latin American labor-based parties adapted successfully to the challenges of neoliberalism and working class decline. It argues that loosely structured party organizations tend to be more flexible than the bureaucratic structures found in most labor-based parties. The argument is illustrated through an analysis of the Argentine (Peronist) Justicialista Party (PJ). The book shows how PJ's fluid internal structure allowed it to adapt and transform itself from a union-dominated populist party into a vehicle for carrying out radical market-oriented economic reforms.