Populist success was heavily dependent on breakthroughs in just three countries beset by political volatility: the Brexit party in the UK, Matteo Salvini's far-right League in Italy, and Jean-Luc Mélenchon's radical-left France Unbowed. These groups will remain divided in the European parliament, blunting their influence. But their greater numbers in Brussels and Strasbourg, combined with the deepening fragmentation of European politics, will make it harder for traditional parties to find a majority.