This study investigates how, and to what extent, citizens use Twitter as a platform for political mobilization in an electoral context. Conceptualizing political participation as a process, we develop a typology of political participation designed to isolate mobilizing calls for action from the rest of the political discussion online. Based on Twitter data collected one week prior to the 2015 British general election, we then identify the top 100 most retweeted accounts using the hashtag #GE2015, classify them by actor type, and perform a content analysis of their Twitter posts according to our typology.

Our results show that that citizens – not political parties – are the primary initiators and sharers of political calls for action leading up to the election. However, this finding is largely due to an uneven distribution of citizen-driven mobilizing activity. A small number of highly active users, typically supporters of nationalist parties, are by far the most active mobilizers in our dataset. We also identify four primary strategies used by citizens to enact mobilization through Twitter: in-text calls for action, hashtag commands, sharing mobilizing content, and frequent postings. Citizens predominantly expressed political calls for action through Twitter’s hashtag feature, a finding that supports the notion that traditional conceptions of political participation require nuance to accommodate the new ways citizens are participating in the politics of the digital age.