Using an innovative survey of six major street demonstrations in Mexico City between 2011 and 2013, this study compares political attitudes of protest participants and nonparticipants. The analysis offers three relevant findings. The results suggest that in comparison to protest nonparticipants, demonstrators tend to be more politically involved and experienced individuals, mobilized through their personal and organizational networks. The intensity of these factors’ effects as protest participation predictors varied across demonstrations, showing that protest participation is triggered by different factors. And the diversity of mobilizing factors shows that protest participation in Mexico City is complex, and is a common form of political participation for the plural, mobilized civil society.