One foot in parliament, one in the streets: Studying the effects of party support in protest participation in six European countries.

Do institutional actors influence participation in street protests? During the last years, increasing attention has been paid to the relationship between electoral and non-electoral forms of participation. Political participation beyond the voting booth has become so ubiquitous that some authors have argued that we currently live in a protest or social movement society. Moreover, so-called movement parties, institutional actors with origins in or strong connections to street politics, have received increasing electoral support across (or beyond) the ideological left-right spectrum. In some cases, movement parties have even become governing parties in countries like Germany (Bündnis 90/Die Grünen), Italy (M5S), Romania (USR-PLUS), and Spain (Podemos). Given that non-electoral politics are increasingly important for institutional actors, we ask: does party support influence participation in protest actions? Do certain parties endorse street mobilizations more than others? When parties show support for a contentious episode, does this influence the participation of their supporters? To answer these questions, we combine survey data and digital media data in three different analytical steps: First, we present data from nationally representative surveys in six countries (Denmark, Germany, Hungary, Italy, Romania, and the UK) on the relationship between party support and participation in several prominent episodes of contention in each country. These surveys collect data about electoral and non-electoral participation patterns between 2015 and 2021. Using regression analyses, we test the effect of different predictors for protest participation, including past and present party support. With that, we test the hypothesis that movement party supporters are more likely to participate in protests. Second, we turn our attention to political parties’ calls for mobilization for said episodes of contention. To do so, we use a combination of automated (dictionary-based) and manual content analyses of parties’ communication on Twitter and Facebook. For that, we collect all tweets and Facebook posts from the official party accounts of the main parties in each country, including movement parties, between 2015 and 2021. We argue that social media platforms are a key venue for parties’ interaction both with their voters and with civil society organizations and hence provide a good proxy of the communication strategies of political parties, particularly in reference to non-electoral politics. Thus, identifying tweets and posts that reference specific episodes of contention allow us to code if, when, and how different political parties refer to specific protests, e.g. through calls for action or critique. Third, we combine these findings with the survey data to test how party support for contentious episodes and individual voting preferences interact in explaining protest participation. We hypothesize that movement party supporters are more likely to participate in protest actions supported by their party but not in other episodes of contention. We expect that this “endorsement effect” is not significant for traditional parties’ supporters. Thus, our paper provides data about the relationship between electoral support and non-electoral participation, as well as political parties’ involvement with non-electoral forms of participation. Moreover, this analysis answers the crucial question of whether party support has an impact on party supporters’ protest participation.