Polish nationalist opposition candidate Karol Nawrocki won the second round of the country’s presidential election with 50.89 per cent of the votes, the electoral commission said early on Monday, in a blow to the reform agenda of the pro-European government.

His rival, Rafal Trzaskowski, the liberal Warsaw mayor and an ally of the government led by Donald Tusk, got 49.11 per cent. An exit poll on Sunday had shown Trzaskowski winning with a razor-thin majority.

Nawrocki, 42, a eurosceptic historian who ran a national remembrance institute, campaigned on a promise to ensure economic and social policies favour Poles over other nationalities, including refugees from neighbouring Ukraine.

The amateur boxer won despite his past dominating the last days of the presidential campaign – from questions over his acquisition of a flat from a pensioner to an admission that he took part in orchestrated brawls.

While Poland’s parliament holds most power, the president can veto legislation, and the vote was being watched closely in Ukraine as well as Russia, the United States and across the European Union.

Nawrocki, supported by the Law and Justice party (PiS), is expected to continue the policies of his predecessor, President Andrzej Duda, also an ally of the largest opposition party, including blocking any attempts by the government to liberalise abortion or reform the judiciary.

On social media platform X, Duda thanked Poles for going to vote in large numbers. Turnout was 71.31 per cent, the electoral commission said, a record for the second round of a presidential election.

“Thank you! For participating in the presidential elections. For the turnout. For fulfilling your civic duty. For taking responsibility for Poland. Congratulations to the winner! Stay strong Poland!” Duda wrote.