By Rob Picheta, CNN

(CNN) — 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.

Karol Nawrocki, the candidate aligned with Poland’s right-wing populist Law and Justice (PiS) party, won 50.89% of the vote, defeating the liberal mayor of Warsaw Rafał Trzaskowski – long the favorite to win – in a head-to-head run-off.

The result extends PiS’ 10-year occupancy of the presidential palace and could spell disaster for Prime Minister Donald Tusk, whose pledge to erase PiS’ fingerprints from Poland’s embattled institutions saw him clash repeatedly with the outgoing President Andrzej

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