News Sharing by Party Line? An Analysis of Source Sharing Patterns in Political Social Media Discussions

In the current media environment, getting political news via social media is common practice. While much research has focused on the effects of getting news via social media, mostly based on the selective exposure hypothesis, less is known about the supply side of news sharing on social media sites, especially concerning politicians' and regular users' sharing behaviour. We argue that observing news sharing patterns can be used to draw inferences about (a) a user's or community's news diet and shared media reality, but also about (b) political communication strategies based on news articles as "opportune witnesses" in political discussions. Theoretically, two opposing sharing strategies can be derived from previous literature on the relationship between politicians and the media: (1) Politicians and party officials selectively share news articles that directly or indirectly favour their positions, either by supporting party policies, or by endorsing candidates. Such a strategy will lead to a positive alignment of media outlets and candidate/party pages, especially when overall political parallelism is high. From an audience perspective, this pattern will reinforce existing selective exposure according to party preferences. (2) Alternatively, recent studies on populist politicians' social media communication suggest that a large part of their posts are critically engaging with news articles, from pointing out errors and posting rebuttals to straight-up accusations of "fake news" and "Lügenpresse". In this setting, media sources are referred as antagonists, which is a frequent strategy in populist communications. This strategy would lead to a reversed alignment of media outlets and party preferences and will lead to a more diverse (and polarized) exposure among the followers. The aim of the present study is to investigate how parties and politicians use references to news in their (strategic) social media communication, and whether and how the respective user communities use the same or different sharing patterns. Drawing on a sample of all posts and user comments posted between July and December 2017 on n = 372 German political Facebook pages (parties and candidates), we used hierarchical Bayesian Poisson scaling to simultaneously estimate the positions of (a) the Facebook pages, (b) their user communities, (c) the respective political parties, and (d) the quoted media outlets. Between 30 and 60 percent of all links posted by parties and candidates referred to a news outlet, indicating the importance of news sharing for political communication on social media. The scaling model reproduced the established left-right positions of all seven major parties (from left to right: LINKE, GRÜNE, SPD, FDP, CDU, CSU, AFD) based only on the media sources which were referred to on their pages. The source sharing patterns of the user communities were overall more centrist compared to the source selection of the professional communicators, who curate the discussions on the pages. Our findings suggest that source selection of professional political communicators follows a latent party line, speaking in favor of the instrumental selection of sources as opportune witnesses. The pattern is less pronounced for the parties Facebook communities, who showed greater overlap in their source sharing repertoires.