A historian and populist firebrand who boasted about his brawls with soccer hooligans has narrowly won Poland’s presidential election, in a political upset that could torpedo the centrist government’s efforts to unspool the legacy of authoritarianism in the country.

Nawrocki won a knife-edge vote that pitted him against Warsaw Mayor Rafal Trzaskowski, who was supported by the ruling centrists Civic Coalition (KO), dealing a major blow to the pro-European governm...

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