Several scholars argue that Europeanization, by transferring political authority to non-partisan supra-national institutions, leads to depoliticization, and even party system cartelization, at the national level. Other scholars, however, maintain that European integration instead is likely to boost partisan conflicts over time. This article tests these rival hypotheses – depoliticization or politicization – using a case study of Swedish European Affairs Committee between 1995 and 2012. If Europeanization results in depoliticization and a waning of opposition, the article argues that the Swedish experiences are likely to confirm this tendency. Yet, in contrast to these expectations, the article presents evidence indicating that partisan struggles on Europeanization in Sweden – particularly on issues of relevance to the left-right divide – has intensified significantly over time. Therefore, the article  casts a shadow of doubt over the hypothesis of depoliticization, as well as over the influential cartel party thesis, while instead supporting the rival hypothesis of increased politicization.