If nationalists keep the momentum in the run-up to the European Parliament elections, the European Union will never be the same again. When voters go to the polls this May to choose a new European Parliament, an event that in the past has barely provoked a yawn, that larger idea will be at risk – not the euro or the single market, and not the EU itself, but the post-Cold War conception of a federated space with harmonized policies on core issues and a joint commitment to democracy and the rule of law.