The election results, based on 99 percent of the votes counted, were not final and can be challenged by Mr. Duda’s opponent.
President Andrzej Duda of Poland appeared on Monday to have narrowly won a second term in the closest presidential election since the end of communist rule in 1989, although the results could still be challenged if his opponent challenges the result by claiming voters’ rights were infringed.
If the decision stands, Mr. Duda will be able to continue on the path set by a conservative nationalist government that has fought to control the courts and media, while stoking fear of gay people, the European Union, foreigners and, recently, Jews.
Mr. Duda fended off a fierce challenge from Rafal Trzaskowski, the liberal mayor of Warsaw. The country’s electoral commission said that with 99 percent of the actual vote counted, Mr. Duda had secured 51.21 percent of the vote. Mr. Trzaskowski won 48.79 percent.
Marcin Matczak, a constitutional expert who has been critical of the sweeping changes to the judicial system, said that the courts would get involved if there is a claim of an infringement by either party, and that it would not be hard for either side to find grounds to do so.
Mr. Trzaskowski, he said, could point to obstacles to voting abroad because of the coronavirus pandemic and the use of public television propaganda against him.
“We still do not have full numbers, so the official result cannot be announced,” said Sylwester Marciniak, the head of the Polish Electoral Commission, although he suggested the result would not change.
