National political parties and European integration

We test competing explanations for party positioning on the issue of European integration over the period 1984 to 1996 and find that the ideological location of a party in a party family is a powerful predictor of its position on this issue. Party family is a stronger Influence than strategic competition, national location, participation in government, or the position of a party's supporters, We conclude that political parties have bounded rationalities that shape how they process incentives in competitive party systems. Political cleavages give rise to ideological commitments or "prisms" through which political parties respond to new issues, including European integration.