The 1947 upheavals on haciendas outside La Paz were facilitated by a coalition between indigenous peasants and urban anarchists. Three factors were essential to this alliance. First, the urban anarchists’ own politics – their libertarian socialist vision, their attentiveness to both “ethnic” and “class” demands, and their organizational federalism – proved conducive to coalition building. Second, prior rural mobilization had created local leaders and networks that would form the rural bases for the coalition; those rural actors would also help to redefine the urban anarchist left, conferring it with a more antiracist and autonomist emphasis. Third, a series of coalition brokers bridged traditional divides of language, ethnicity, and geography. This account qualifies common dismissals of the Bolivian left as mestizo-dominated and class-reductionist while also illuminating the process through which the alliance developed. It concludes that ideologies and human decisions are often just as important as structural circumstances in determining the potential for popular coalitions and militant mobilization.