Voters are going to the polls in the Netherlands in the first of three crucial eurozone elections this year.
The race is dominated by Prime Minister Mark Rutte's centre-right party and that of Geert Wilders, running on an anti-immigration platform.
Mr Rutte has said the election is an opportunity for voters to "beat the wrong sort of populism".
Mr Wilders has pledged to take the Netherlands out of the EU, close all mosques and ban the Koran.
His Freedom Party had been leading in opinion polls but they have since suggested his support may be slipping.
France goes to the polls next month to elect a new president while Germany is due to hold a general election in September.
While a populist surge is still possible in the Dutch ballot, a host of other parties could also do well, leaving Dutch politics fragmented, the BBC's Damian Grammaticas reports from The Hague.
As parliamentary seats are allocated in exact proportion to a party's vote share and no major party wants to be in a coalition with Mr Wilders, he has little chance of entering government however well he performs, our correspondent says.
In the run-up to the vote, party leaders took part in televised debates, with Mr Rutte and Mr Wilders clashing over how to stem immigration.
Mr Rutte dismissed Mr Wilders's plan to close borders and mosques and to ban the Koran as "fake solutions". Mr Wilders accused Mr Rutte of providing better healthcare for immigrants than for the Dutch themselves.
Lodewijk Asscher of the Labour Party, the junior party in Mr Rutte's coalition, called Mr Wilders a man of "10,000 angry tweets and no solutions".
One opinion poll suggested that the spat, and the riots in Rotterdam, had given anti-immigrant parties a boost.
Wednesday's election is expected to be followed by protracted coalition talks.
Analysts say a strong showing for Mr Wilders could foreshadow next month's presidential election in France, where far-right, anti-EU contender Marine Le Pen has widespread support.
In Germany, another right-wing party, Alternative for Germany, is expected to win seats for the first time in September.