In this investigation we describe a population of politically-charged social media users we call serial activists. We mined 20M tweets related to nearly 200 instances of political protest between 2009 and 2013 and identified a network of users tweeting across geographically distant protest hashtags. We resorted to statistical disambiguation to describe the characteristics of this group, which have an ordinary following but bridge disparate language communities and facilitate collective action by virtue of their dedication to a cause. After exploring how serial activists deviate from traditional forms of political activism, we report on a series of in-depth, semi-structured interviews held with 21 such activists. The material was thematically-coded to provide a typology of serial activists and their struggles with institutionalized power, political activism, and social media in the context of political turmoil. This research provides a bridge to the qualitative-quantitative gap in the social sciences by resorting to an ethnographic embedment of big data observations in the lifeworld of political activists.