For decades, the disparate right-wing parties of Europe have sought to reverse the seemingly inevitable leftward march of the continent. They have campaigned on platforms promising to liberate their national polity from the perils of globalization and the immense, tangled bureaucracy of Brussels. The past half-decade has seen these parties creep ever closer to victory.Reform UK, the British party founded by Nigel Farage and running on an anti-immigration platform, is sitting in a comfortable lead over both establishment rivals. Alternative for Germany, a party deemed so right-wing by its opponents that mainstream lawmakers refuse to work with it, is dominating...