Social networking sites have become a major gateway for citizens to engage with political content. Citizen-users are able to produce and share messages in a one-to-many manner that can reach other citizens but also media organizations, politicians and institutions. At the same time, social media provides a platform enabling communication flows beyond nationally-defined public spheres. In light of these recent transformations that encourage citizens to be more than mere spectators of national news produced by traditional media actors, our paper has two aims. One is to provide a categorization of user-generated political communication and forms of citizen engagement on social media. The other is to discuss variations in the way transnationalization processes occur at different levels of political engagement. We underlie a basic distinction of three styles of content: factual, ideological and moral. The factual style is the production of news narratives alternative to those of the mainstream media. The ideological style is taking a politically biased stance in order to comment and mobilize around a given set of ideas. The moral style is the attribution of responsibility, blame, or appeal to solidarity in relation to a moral cause. Moreover, online users can engage with the different styles of political content through four degrees of engagement: making, interpreting, diffusing and listening. We consider Facebook and Twitter as the two principal social media platforms through which a transnational online sphere of political communication is constituted, and we discuss how their different technological designs encourage different styles and degrees of political engagement. We also suggest that the way messages from one national context are being shared and discussed outside the national sphere differs with regard to the type of content, the degree of user engagement, and the medium used for communication.
