The Hashtag Election? Social Media in the 2015 UK General Elections

Social media has radically changed the political information environment, including the types of content the public is exposed to as well as the exposure process itself. Individuals are now faced with a wider range of sources (social and traditional media), new socially mediated and selective patterns of exposure, and alternate modes of content production (e.g. user-generated content). The 2015 British general election, often referred to as the “hashtag election” was characterized by the highest levels of online campaigning across all parties. However, the relevance of social media throughout the campaign, its relation to traditional media and its ability to mobilize supporters and influence public opinion is still a matter of scholarly debate. Using linked newspaper and Twitter data, as well as survey data collected during the campaign, this paper identifies the most relevant topics and issues in the 2015 UK general elections, tracks their evolution on social and traditional media and measures their effects on public opinions and attitudes. We use an ensemble learning method with output from multiple supervised and unsupervised models to identify major topics and events in the campaign, and label traditional and social media content according to them. We then employ a Granger-causality framework to test whether social media follows traditional media or on the contrary, topics which gain popularity on social media are then covered by traditional media. We test the robustness of our findings by tracking the links to newspaper articles which were shared on social media, as well as mentionings of social media sources in newspaper articles. Finally, we rely on public opinion surveys to assess the agenda-setting effect of each type of media.