In July 2006, following contested electoral results and suspicions of fraud, L?pez Obrador, the losing candidate of a left-wing coalition with the Revolutionary Democratic Party (PRD) at its heart, chose to protest by camping out on the central square (El Z?calo) in Mexico City and in parts of downtown. This form of protest was grounded in a rich repertoire of traditional forms of protest, and it drew in particular on a movement against electoral fraud that emerged in the 1990s under the banner of the PRD. This paper seeks to identify the factors explaining how Obrador?s 48-day camping operation succeeded in maintaining a high level of mobilization among supporters and how this mobilization fueled and was fueled by specific forms of activist sociability. Moreover, without PRD?s strong local and national networks, it would have been difficult to implement and maintain this form of protest. We show that these networks were maintained by incentive systems and awareness campaigns and that they helped sustain L?pez Obrador?s political charisma and enable the long-term survival of the protest movement.