Responsive voters–how European integration empowers Eurosceptic parties

European integration has been progressing even as support for Eurosceptic parties has been rising. Post-functionalist literature focuses on how public attitudes affect the progress of European integration (bottom-up), but the mechanism through which European integration affects domestic politics (top-down) is underexplored. Extreme parties on either the left or right are known to adopt a Polity-Eurosceptic agenda in order to realign the main domestic political cleavage and turn themselves into the new mainstream. We aim to contribute to this literature by arguing that the timing and type of EU events matter. Specifically, the vote for such Eurosceptified Pariah Parties increase with integration events that have a potential for high media profile, signal reduced state autonomy, and occur in proximity to national elections. Furthermore, we argue that even if mainstream parties may counter Eurosceptified Pariah Parties’ claims, the net effect is to ratchet-up electoral support for the latter. We support this argument by employing a mixed-method design using both a natural experiment approach (UESD for Spain’s 1993 election) and a model-based approach (all parties in 1979–2017 and a new event database). Results are robust to the usual confounders, and the exclusion of different classes of events and opportunistically-timed elections.