Eurosceptic Nawrocki's win can deliver considerable setbacks to former European Council President Tusk's pro-EU government.

US Homeland Security Secretary Kristi Noem urged Poles to vote for the nationalist opposition candidate in Sunday’s presidential election, wading into a tightly-contested campaign that threatens to derail efforts to rebuild the country’s democratic institutions.

Karol Nawrocki, a historian who has flaunted his ties with the U.S. president, has promised to block a Ukrainian accession to NATO.