This article analyzes the impact of party strategies on the issue structure, and consequently the dimensional structure, of party systems across Europe. Conceptualizing political competition in two dimensions (economic left-right and social traditionalism versus liberalism), the authors demonstrate that political parties in both Eastern and Western Europe contest the issue composition of political space. The authors argue that large, mainstream parties are invested in the dimensional status quo, preferring to compete on the primary dimension by emphasizing economic issues. Systematically disadvantaged niche parties, conversely, prefer to compete along a secondary dimension by stressing social issues. Adopting such a strategy enables niche parties to divert voter attention and challenge the structure of conflict between the major partisan competitors. The authors test these propositions using the 2006 iteration of the Chapel Hill Expert Surveys on Party Positions. Findings indicate that while the structure of political conflict in Eastern versus Western Europe could not be more different, the logic with which parties compete in their respective systems is the same. The authors conclude that political competition is primarily a struggle over dimensionality; it does not merely occur along issue dimensions but also over their content.