Do European Parliament elections foster challenger parties' success on the national level?

European Parliament elections create structural advantages for challenger parties. Building on the second-order elections theory, this article argues that European Parliament elections foster challenger parties' success on the national level by increasing their visibility and offering an opportunity structure for domestic politicisation of Europe. I test this proposition by exploiting the quasi-exogenous timing of European Parliament elections and the variation in national electoral cycles since 1979. A country-fixed effects model and two placebo-tests show that populist radical right parties gain momentum in the supranational contest, particularly when coinciding campaigns increase the domestic salience of Europe. Considering their antagonism to an integrative Europe, it seems ironic that the European Parliament elections foster the ascendency of just these opponents of the European idea