How Europe's surging populist right is reshaping the political establishment

From the upper floors of Millbank Tower, a skyscraper overlooking the River Thames in London, the U.K. Houses of Parliament are just a few hundred yards away. For decades, the building housed the headquarters of Britain's Conservative Party, one of the world's oldest political parties. Today, it is home to Reform UK, the right-wing populist party led by Nigel Farage that is hoping to — and by some measures may already have — replace the Conservatives as the dominant force on the British right. The change of occupants reflects a wider political upheaval sweeping some of Europe's biggest democracies. In...