Romanians vote in a presidential election runoff on Sunday that could see Calin Georgescu, a far-right critic of NATO, defeat pro-European centrist Elena Lasconi, an outcome that might isolate Romania in the West and erode its support for Ukraine.

Romanians are voting in a parliamentary election sandwiched between a two-round presidential race. The first round plunged the European Union and NATO member country into unprecedented turmoil following allegations of electoral violations and Russian interference.

Romanian centrist and leftist parties looked to have fended off a surge by the nationalist right in Sunday's parliamentary election, as attention turned to a top court ruling later on Monday on whether to annul the results of a presidential vote.

Romania's Constitutional Court on Monday validated the shock first-round result in its presidential election, setting the stage for a run-off vote on Dec. 8 that could upend the country's pro-Western orientation and erode backing for Ukraine.

Romania's ruling center-left Social Democrats were poised to secure the most votes in Sunday's parliamentary election, according to preliminary results published Monday.