The Treaty of Maastricht signified an end to the permissive consensus that had characterised the first decades of the European integration project: the European Union (EU) as a political issue not only became more salient, but also aroused more public discontent. From the perspective of the political elite, the 1990s were a decade of optimism focused on deepening and widening the European project, with, for example, the imminent introduction of the euro and the EU enlargement with central and eastern European countries. At the level of the general public, European integration became increasingly contested, and claims about a ‘democratic deficit’ of the EU became ubiquitous. Although the Maastricht Treaty was not the starting point,1 it substantially amplified the democratic debates about the EU.