Abstract. As the European Union (EU) has evolved, the study agenda has shifted from ‘European integration’ to ‘EU politics’. Missing from this new agenda, however, is an understanding of the ‘cognitive constraints’ on actors and how actors respond, i.e. the shape of the EU ‘political space’ and the location of social groups and competition between actors within this space. The article develops a theoretical framework for understanding the shape of the EU political space (the interaction between an Integration–Independence and Left–Right dimension and the location of class and sectoral groups within this map), and tests this framework on the policy positions of the Socialist, Christian Democrat and Liberal party leaders between 1976 and 1994 (using the techniques of the ECPR Party Manifestos Group Project). The research finds that the two dimensions were salient across the whole period, explains why the party families converged on pro–European positions by the 1990s and discovers the emergence of a triangular ‘core’ of EU politics.