Frans Timmermans, the Socialist candidate for European Commission president, said Friday that a surprise first-place finish in his native Netherlands would propel his party to victory all across Europe.

Exit poll numbers show Timmermans' Labor Party finishing on top Thursday night. The Netherlands and the U.K. were the first to vote in the European Parliament election, which runs across Europe until Sunday.

It was an unexpectedly strong showing that placed the Socialists ahead of Prime Minister Mark Rutte's liberal People's Party for Freedom and Democracy, and well ahead of the far-right Forum for Democracy party led by Thierry Baudet.

The Dutch outcome must still be confirmed by official results, but Timmermans, who is first vice president of the Commission and a former Dutch foreign minister, saw the victory as a sign that the center left is gaining momentum across the Continent.

"Thank you," Timmermans said in Dutch again and again, in a video posted by his campaign on Twitter. "It is a signal that has been picked up all across Europe."

It is far from clear that the outcome in the Netherlands will influence voters elsewhere in Europe.

With most European countries voting Sunday, Timmermans barnstormed on Friday from Barcelona to Milan in a last burst of campaigning that was to bring him to Vienna on Saturday and finally back to Brussels. His main rival, Manfred Weber of the center-right European People's Party (EPP), held a rally Friday evening in Munich with German Chancellor Angela Merkel, Croatian Prime Minister Andrej Plenković and Bulgarian Prime Minister Boyko Borisov.

Supporters of Weber said that the Socialists' early enthusiasm is exaggerated and misplaced, and they predicted that the EPP would once again finish first overall with the largest number of seats in the European Parliament.

"We are confident," said Antonio López-Istúriz White, the secretary-general of the EPP. "We will remain to be the first force."

López-Istúriz White predicted that the EPP would hold 180 or more seats in the 751-member Parliament — down from its current 216, but still more than other groups. (POLITICO's projections put the EPP first at 169 seats, with the Socialists following in second place at 150 seats.)

He also said the Socialists' hopes of capturing the top spot are tied to the Labour Party in the U.K., which he described as a dicey proposition in the era of Brexit.

"What is the quality of the members of the Labour Party that are going to come to the European Parliament?" he asked. "Are they going to be pro-European? Are they going to vote with the Socialist group in the European Parliament? There are lots of questions."

It is far from clear that the outcome in the Netherlands will influence voters elsewhere in Europe, but a bad showing for Timmermans and his party in his home country would have been a stinging embarrassment and potentially devastating for his aspirations for a senior EU post. The first-place finish, if confirmed, gives a boost not just to Timmermans and the Socialists but also to defenders of the Spitzenkandidat or "lead candidate" system.

Leaders on the European Council, who must propose a new Commission president for confirmation by the European Parliament, have said they will not be bound by the Spitzenkandidat system, which envisions them picking one of the lead candidates in the election from the pan-European party groups — most likely the candidate whose group wins most votes.

But the possibility that attention around Timmermans' campaign raised interest in his home country, and helped beat back Baudet's far-right Forum for Democracy, will give ammunition to defenders of the system, who say it helps generate greater public interest and awareness.

Turnout in the Netherlands was also projected to be higher this year than five years ago, climbing to 41.2 percent compared to 37.3 percent in 2014.

French President Emmanuel Macron, one of the critics of the Spitzenkandidat system, is hoping to create an alliance between his new centrist-liberal group, the Socialists, the Greens and other parties, while pressuring the EPP to make concessions in the negotiations over how to fill the senior EU leadership posts.

""After the elections, heads cool. We hope and expect that we can unite with Manfred. He has the plan" — Antonio López-Istúriz White, secretary-general of the EPP

Currently, the EPP holds the presidencies of the Commission, Council and Parliament — a monopoly on the main institutions that the Liberals and the Socialists want to break.

An official with Macron's Renaissance list of candidates called Timmermans' victory in the Netherlands "good news" — noting both Timmermans' party and Rutte's liberals are solidly pro-EU.

"He won with the liberals, as the grand European voice — that’s what we are in France," the official told POLITICO.

But López-Istúriz White, the EPP secretary-general, questioned if Macron's liberal force and the Socialists would be able to unite behind a candidate for Commission president. By contrast, he predicted, EPP leaders would appear at a summit in Brussels next Tuesday, before a European Council that evening, and demonstrate their unified support for Weber.

He also said that Weber has a plan to unite all of the pro-EU political groups into a majority coalition. "After the elections, heads cool," he said. "We hope and expect that we can unite with Manfred. He has the plan."