Why do some new policy issues influence voters’ decisions at the ballot box while others do not? This study develops and tests arguments about the way in which supply-side factors, i.e. the behavioral characteristics of political parties, mediate the extent to which new and complex policy issues affect voting behavior. Specifically, it proposes a model, i.e. the issue voting triangle, that draws attention to three supply-side factors that explain variation in issue voting: (1) issue linkage, (2) issue mobilization and (3) issue competition. The degree of issue voting is expected to vary as a result of the linkage between parties’ positions on the new policy issue and the main dimension of political conflict (issue linkage), the extent to which parties take diverging stances on the new issue (issue competition) and the degree to which parties view the new issue as important (issue mobilization). These general propositions are tested by examining the impact of the European integration issue on vote choice in British, Danish, Dutch and German elections between 1992 and 2002. The empirical analysis demonstrates that issue voting on the basis of a new and complex policy issue is indeed more prominent when the three issue voting triangle conditions are present. Consequently, this study has crucial implications for the study of elections and voting behavior and enriches our understanding of the issue voting process.