BRUSSELS The European Union's marathon parliamentary election kicked off on Thursday when Britain and the Netherlands voted, with right-wing, anti-EU parties expected to attract a surge of protest votes in many countries on a low turnout.
However, a Dutch exit poll indicated that the anti-Islam, Eurosceptic Freedom Party of Geert Wilders' - which plans to forge an alliance with France's far-right National Front - had fallen well short of its goal of topping the poll.
After two months of campaigning that opinion polls suggest has largely failed to inspire the electorate, some 388 million Europeans are entitled to vote in 28 countries, choosing 751 deputies to represent them in the European Parliament.
Despite efforts to mobilize voters by telling them they will for the first time indirectly be choosing the next president of the European Commission, pollsters forecast a low turnout, possibly below the 2009 nadir of 43 percent.
With Europe struggling to recover from economic crisis, including record high unemployment and negligible growth, the election is expected to produce a surge in support for Eurosceptics on both the far-right and hard left.
In Britain, final opinion polls showed the UK Independence Party, which wants to withdraw from the EU and impose tighter immigration controls, topping the poll and pushing the governing Conservatives into third place behind Labour.
If confirmed, that could raise pressure on Conservative Prime Minister David Cameron, who has promised an in/out referendum on EU membership in 2017 if he is re-elected next year, to take a tougher line on reducing the EU's powers.
In the Netherlands, an IPSOS exit poll on public television suggested Wilders' Freedom Party would finish fourth with 12.2 percent, behind three pro-European parties, the center-right Christian Democrats, the centrist Democrats 66 and Prime Minister Mark Rutte's liberals.
Wilders blamed the disappointing score on a low turnout, saying that "by staying home (voters) showed their loathing for and disinterest in the European Union. The Netherlands has not become more pro-European."
In the last European Parliament elections five years ago the Freedom Party came second. Andre Krouwel, a political science professor at Amsterdam's VU University, said Wilders had failed to get enough of his supporters to turn out.
"His support isn't down, around one third of the electorate agrees with him - but that one third didn't show up," he said. "That's bad news for him, because he wanted to portray himself as a victor ... That would have given him status in Europe."
Both the Netherlands and Britain will report their results once voting has finished in all EU member states on Sunday.
Consolidated results, including the allotment of seats in the parliament, will be announced at around 2100 GMT on Sunday.
The bulk of countries vote on Sunday, when the trend towards the political extremes may become clearer, particularly in France, Denmark, Hungary, Italy, Greece and Austria.
At one of his final campaign events, Jean-Claude Juncker, the top candidate for Europe's center-right political group, urged voters to steer away from the extremes.
"Do not give your votes to extremist xenophobes or fascists," the veteran former Luxembourg prime minister said at a rally in Brussels. "If you want Europe to function and to serve its citizens, we should vote for people who will work hard in the next European Parliament."
Juncker and his Socialist opponent, Martin Schulz, the German president of the outgoing European Parliament, have held an unprecedented series of television debates in an effort to personalize the election and enthuse the electorate.
LOW TURNOUT FAVOURS EXTREMES
Since the first direct elections to the European Parliament were held in 1979, turnout has fallen every time. It is expected to drop again to around 40 percent this year, pollsters say, a factor that will tend to boost the vote for radical parties.
Turnout in the Netherlands was roughly unchanged from 2009 at about 37 percent, the exit poll showed. The poll of 40,000 voters did not give a margin of error.
Europe's mainstream political groups - the center-right European People's Party, the center-left Socialists & Democrats, the liberal ALDE alliance and the Greens - are together expected to secure 70 percent of the vote, leaving them as a driving force in Europe as long as they work together.
In France, ex-President Nicolas Sarkozy, absent from daily politics since being defeated in 2012, intervened at the last minute in the campaign as his conservative UMP party risks being beaten into second place by Marine Le Pen's National Front.
In an implicit swipe at his unpopular Socialist successor, Francois Hollande, Sarkozy called for a radical shake-up in the way the EU is run, with a Franco-German economic zone taking leadership of the euro zone at the center of Europe.
He also called for the suspension of the EU's open-border Schengen zone of passport-free travel, which had failed to prevent an influx of migrants, and its replacement by a stricter pact open only to countries with tougher immigration controls.
Sarkozy also said in an article in the French weekly magazine Le Point and the German daily Die Welt that it was time to put an end to what he called the "myth" of equality of member states, citing euro zone minnows Luxembourg, Malta and Cyprus.
Once derided as a toothless talking shop, the European Parliament has gained relevance since the passage of the Lisbon Treaty in 2009 and now enjoys 'co-decision' powers with member states over most legislation.
For the first time, parliament has also backed the idea that each group should have a "Spitzenkandidat" - German for "top candidate" - who is in line to become president of the European Commission should their group win the elections.
While supporters of the process are adamant it should be used to determine who succeeds Jose Manuel Barroso as Commission president, one of Brussels' most influential jobs, EU leaders are ultimately responsible for putting forward a name.
According to the Lisbon Treaty, they must "take into account" the election results in making the nomination, and that person must then be approved by a majority in parliament.
If EU leaders and parliament cannot agree on the candidate, there is the risk of an institutional impasse in Brussels, which could have long-term repercussions on confidence in the EU among already disillusioned voters and financial markets.
Parliamentary leaders will meet on the morning of May 27 to assess the outcome of the elections, and EU heads of state and government will do the same over dinner the same day. But there is not expected to be any clarity on the nominee for Commission president until later in June, EU officials say.
While the main Eurosceptic assault in many countries comes from the far right, the challenge to new Italian Prime Minister Matteo Renzi's center-left Democratic Party comes from the anti-establishment 5-Star Movement of former comic Beppe Grillo.
The last surveys released before a blackout on publishing opinion polls gave the Democrats a comfortable lead, but private polls leaked since then suggest it may be a tighter race.
(Additional reporting by Anthony Deutsch in Amsterdam, John O'Donnell and Julia Fioretti; Writing by Luke Baker and Paul Taylor; Editing by Will Waterman and David Stamp)