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 conservative Trump-backed candidate in Poland's runoff election, has narrowly won the presidential race. Charles Kupchan, a senior fellow at the Council on Foreign Relations, breaks down how the election results may affect NATO and Poland's relationship with the European Union.