Conservative Karol Nawrocki has won Poland’s weekend presidential runoff election, according to the final vote count.

WARSAW—Exit polls in Poland’s presidential election predicted a slim victory for a conservative historian who had been given a nod of support by President Trump and is a backer of the former ruling Law and Justice party,

A vote seen as a test of the power of populist nationalism in Europe was too close to call, with exit polls putting the two contenders neck and neck.