A nationalist candidate backed by Donald Trump secured victory in Poland’s presidential election, defeating the centrist mayor of Warsaw in a contest that could stymie the government’s efforts to shift the nation back into the European Union mainstream.

With Karol Nawrocki elected president, the conservative Law and Justice party retains its ability to block the agenda of pro-E.U. prime minister Donald Tusk.

The victory of nationalist Karol Nawrocki in Poland's presidential election looks set to strain relations with Ukraine and embolden Donald Trump-inspired conservatives in central Europe, analysts and diplomats said on Monday.