This paper applies categories developed in the classic literature on political opposition to the developing European Union. It is clear that the EU has never developed the third great milestone identified by Dahl in his analysis of the path to democratic institutions. That is, we still lack the capacity to organize opposition within the European polity. This failure to allow for opposition within the polity is likely to lead either (a) to the elimination of opposition altogether, or (b) to the mobilization of an opposition of principle against the EU polity. This problem is also beginning to reach down into the domestic sphere, in that the growing weight of the EU, through its indirect impact on national politics, helps to encourage domestic democratic deficits, hence limiting the scope for classical opposition at the national level. Here too, then, we might expect to see either the elimination of opposition or the mobilization of a new – perhaps populist – opposition of principle.