Unemployed and informal workers seem an unlikely source of large-scale collective action in Latin America. Since 1997, however, Argentina has witnessed an upsurge of protest and the emergence of unusually influential federations of unemployed and informal workers. To explain this puzzle, this article offers a policy-centered argument. It suggests that a workfare program favored common interests and identities on the part of unemployed workers and grassroots associations, allowing them to overcome barriers to collective action. State responses to demands for workfare (...) benefits generated a pattern of protest and negotiation that strengthened those groups and dramatically expanded social policy. (shrink)