The paper analyses the consequences of intra-party conflict over European issues on party strategy in national election campaigns. How strong is the constraining effect of intra-party conflict in election campaigns? Do mainstream parties de-emphasize European issues as a result of internal conflicts and divisions? Based on a new measure for intra-party conflict which emphasizes variance of positions in public debates on European integration issues, we first examine internal divisions within parties in public debates on main European integration steps (e.g. the Maastricht Treaty, the Constitutional Trreaty, the Euro crisis) since the early 1970s. These debates can be taken as perfect opportunities to observe intra-party conflict. In a second step, we analyze party strategies in national election campaigns with regard to European issues. We examine the politicization (or de-politicization) of European issues in national election campaigns in six West European countries (i.e., Austria, Britain, France, Germany, Sweden, and Switzerland) since the early 1970s.