A nationalist candidate backed by Donald Trump won Poland’s presidential election, defeating the centrist mayor of Warsaw and complicating efforts to shift the nation back into the European Union mainstream.

The victory of Karol Nawrocki, who is backed by the previous right-wing governing party, will complicate Prime Minister Donald Tusk’s efforts to advance his liberal agenda.

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.