Contagious populist radical right: The role of issue salience for electoral success in the European Parliament.

A rich literature has revealed the consequences of issue shifts towards topics owned by niche parties in a cross-national context. So far, however, the processes leading to the ownership of certain topics have been mostly disregarded. In addition, the effect of issue shifts in the European Parliament have been much less understood, although the European Parliament has recently seen a dramatic rise of radical right and populist parties (RRPP). We address these research gaps by focusing on direct communications expressed on Twitter by all Members of the European Parliament between 2014 and 2019 (over 3 million Tweets). Moving beyond manifesto data, we, hence, utilize the huge repositories of social media in a quantitative manner to study the salience shifts of parties in reaction to niche competitors. Structural Topic Models allow us to explore empirically the issues RRPP occupy in the European Parliament and to trace their communicative behavior dynamically. In particular, we reveal which parties "appeal broadly", which issues are owned by PRRP and how other parties might adopt issues owned by RRPP. By using Negative Binomial Regressions, we then link the patterns of issue diversity and the level of issue salience to the outcomes of the European Parliament election in 2019. Our results show that communicating about topics owned by RRPP has indeed a positive effect on election results for mainstream and left-wing parties. Other than expected, this effect is not moderated by political ideology. Even more, we observe strong negative effects if RRPP concentrate on typical right-wing issues. We therefore contribute to the literature on party competition and electoral success, issue competition and issue ownership in the European Parliament and add a new methodological approach to study these issues.