Nationalist opposition candidate Karol Nawrocki narrowly won Poland's presidential election, results showed Monday, delivering a major blow to the centrist government's efforts to cement Warsaw's pro-European orientation.

The victory of the nationalist historian Karol Nawrocki in Poland's presidential election is a clear setback for the pro-EU government of Prime Minister Donald Tusk. Many Nawrocki supporters say they want stricter curbs on immigration and advocate conservative social values within the European Union.