The Labour Party of European Commissioner Frans Timmermans on Thursday won a surprise victory in a Dutch election for European Parliament, an exit poll showed, easily beating a Eurosceptic challenger who had been topping the polls.
The leading social democrat candidate to head the EU Commission, Timmermans propelled his pro-European party to an upset win, taking more than 18% of the vote.
The upstart far-right Forum for Democracy of nationalist Thierry Baudet, which had been neck and neck in polls alongside Dutch Prime Minister Mark Rutte's conservatives, finished third at 11%, the exit poll showed.
Labour doubled its 2014 showing and beat opinion polls, most of which showed it finishing third at best.
The Dutch vote was a first test of the appeal of populist and Eurosceptic parties contesting elections across the bloc through Sunday, and the outcome may offer some relief to established pro-EU parties.
"I hope that this gives a tailwind for a lot of other social democrats in Europe," Timmermans said in a reaction to the poll result.
The Dutch result could prove to be an outlier. Far-right parties are expected to increase their standing in the European Parliament, but are not expected to take more than a fifth of seats in the May 23-26 election.
The Netherlands and Britain were the first countries to vote. British polling stations close at 2100 GMT.
A YouGov poll on Wednesday put support for Nigel Farage's Eurosceptic Brexit party, which is campaigning for Britain to leave the European Union, at 37%, with the Conservatives of embattled Prime Minister Theresa May on just 7%.
In France, Marine Le Pen's National Rally leads opinion polls, slightly ahead of President Emmanuel Macron's Republic On the Move party, according to a survey published by Les Echos newspaper on Thursday.
In Germany, Angela Merkel's Christian Democrat party is expected to remain the largest, with the anti-immigrant Alternative for Germany seen at 12%, in fourth place.
Italy's far-right ruling League party, led by Deputy Prime Minister and Interior Minister Matteo Salvini, is seen remaining the country's largest.
In the Netherlands, where turnout rose 4 percentage points from five years ago to 37%, Rutte's People's Party for Freedom and Democracy (VVD), came in second at 14%, according to the Ipsos exit poll, which has a margin of error of 2%.
The Freedom Party of Geert Wilders, another Eurosceptic best known for his campaign against Islam, won 4%, a decade low.
Toby Sterling and Anthony Deutsch of Reuters reported from Amsterdam.