This article investigates the link between attitude formation at the national and the supranational level of the European Union (EU). While the existing studies have provided strong evidence that attitudes towards national institutions fundamentally condition attitudes towards the EU, the mechanisms through which these spillovers occur are not clearly spelled out. Our main contribution is to theorize the complex ways in which the national politicization of the European integration process affects support for the EU by focusing on critical moments in the EU integration process and the electoral fortunes of the political parties doing the cuing. To test our theoretical claims, we employ multilevel models using six rounds of the European Social Survey combined with party-level data from Chapel Hill Expert Survey, and various country-level data. The analyses show that spillover effects are crucially conditioned by the level of politicization of European integration at the national level.