Italians voted Sunday in a landmark referendum that pits the country’s prime minister, Matteo Renzi, against a growing populist movement. The ballot, which proposes changes to the country’s constitution, measures Renzi’s overall performance. The referendum comes as mainstream politicians across Europe face challenges from antiestablishment forces, due to economic disparity and unease over immigration. Austrians also took to the polls on Sunday, to vote in their presidential election between right-wing Norbert Hofer and center-left candidate Alexander Van der Bellen. If Hofer wing, he would be the first right-wing populist leader in Europe since World War II.