The literature has identified the emergence of a transnational cleavage, which has mainly revolved around conflicts over national identity, state sovereignty and international trade. The European integration process has appeared to be a fundamental parcel in this arising cleavage, weakening state prerogatives and allowing free circulation of people and goods. Thus, we posit that the transnational cleavage has been rooted in EU mobilisation emerging within European societies. To find evidence of such emerging cleavage, we analyse new patterns of political behaviour linking social groups and political organisations, focusing on the party-electorate dyad. We consider the conjecture on emergence of the new cleavage confirmed if it is proved that during elections voters are mobilised on the EU, with party positions and salience on the EU working as driving factors of voters’ mobilisation. Therefore, we advance the following hypotheses: H1: Voting behaviour is influenced by the party positions on the EU (EU party position hypothesis). H2: Voting behaviour of electorate is influenced by the salience that parties assign to the EU (EU salience hypothesis). We focus on five Western European countries – Austria, France, Germany, Italy and the Netherlands – which held general elections in period 2017-2018.