Karol Nawrocki, a historian and former boxer, will be Poland’s next president. Nationalist forces in the United States and Europe had been rooting for him: Mr. Nawrocki was supported by President Trump, Prime Minister Viktor Orban of Hungary and George Simion, a right-wing politician in Romania who recently lost a presidential election.

Warsaw’s liberal mayor and his insurgent populist challenger are locked in a dead heat as they fight for the presidency of Poland, exit polls projected after Sunday’s head-to-head vote, leaving the country tilting between two wildly different political futures.

According to the preliminary result of an exit poll prepared by the Ipsos research centre, Rafał Trzaskowski has won 50.3% of the vote. The exit poll's result is, however, within the margin of error and too close to call.

Poland is set to hold a presidential runoff election on Sunday between two candidates offering starkly different visions for the country’s future.