Portuguese President Marcelo Rebelo de Sousa will ask one party leader – likely whichever commands the most votes or seats – to form a government.

Shortly after polls closed, anticipating a win by the center-right coalition led by Luís Montenegro, Chega leader André Ventura reiterated his call for Portugal be governed by “all” its right-wing parties, but Montenegro has ruled out any sort of political agreement with the far-right.

Before the election, the Democratic Alliance had a slight polling lead. Socialist Party leader Pedro Nuno Santos suggested that were he to lose the election, he would be willing to make a center-right government “viable” in order to prevent the country from falling under the political influence of the far-right.

While such a deal would allow Montenegro to assume power and become prime minister, it’s unclear how much a minority executive would be able to depend on the Socialist Party, and how long it would be able to pass legislation without Chega’s support.

The Socialist Party, which looks to have registered its worst results since 2011, could still emerge as the largest party and form a minority government backed by far-left politicians like those of the Left Bloc and the Portuguese Communists.

Turnout for Sunday’s snap vote is on track to be among the highest in decades, with electors turning out in droves to have their say on who will govern the country after the abrupt resignation of Nuno Santos’s predecessor Antonio Costa in the wake of an influence-peddling probe last fall. The full turnout won’t be known for a few weeks, when foreign votes are fully counted.

Should Montenegro’s centre-right bloc form a government, it would mark the end of eight years in power for the Socialist Party. This would come as a blow to Europe’s social democrats, who would govern just four of the EU’s 27 member countries.

Meanwhile, Chega’s strong performance is likely to bolster the far-right groups projected to make major inroads in next June’s European Parliament election.