BRUSSELS: More than 400 million Europeans will be called to vote next week to set the stage as Brussels debates its post-Brexit future and faces a rising populist tide.
Eurosceptic forces are expected to seize ground in the European Parliament, buoyed by popular concerns about immigration, even if few parties want to quit the bloc.
Only in Britain, which voted in June 2016 to quit the union but has yet to decide how and when, are outright anti-European "leavers" expected to do well.
But once-marginal populist and nationalist parties have a new wind in their sails and could win enough seats to trouble Brussels' federalist consensus.
The main centre-right and centre-left blocs in the Strasbourg assembly may have to offer alliances or concessions to populist rivals for the first time.
Voting will begin Thursday in a Britain roiled by parliamentary fighting over how to define Brexit, and Nigel Farage's europhobe Brexit Party leads in polls.
The Netherlands votes the same day, followed by Ireland on Friday, some eastern countries on Saturday then France, Germany, Spain, Italy and the rest on Sunday.
The British result is not expected to change much in Brussels, although a strong showing by the Labour opposition may help the socialist bloc in Europe.
But EU leaders and top Brussels officials will be wary of gains by Italy's far-right League, Spain's emerging Vox and Victor Orban's ruling Hungarian party Fidesz.
In France, Marine Le Pen's far-right National Rally is polling neck-and-neck with President Emmanuel Macron's centrist group, amid populist street protests.
If the vote again gives Le Pen the biggest number of French seats in Strasbourg, it will dent Macron's authority among Europeans as he pushes for closer EU integration.
The 751-member legislature will play a role in the weeks and months after the vote in assigning key leadership roles on the EU Commission and EU Council.
But the horsetrading for top jobs and the nuts and bolts of European legislation have never much excited the electorate - and turnout has been low and falling.
At the last Europe-wide election in 2014, participation fell to 42.6 per cent, down in every cycle since the first such poll in a then much smaller union in 1979.
Enthusiasm was particularly low in some of the newer, eastern members of the union, with turnout in the Czech Republic on only 18 per cent and in Slovakia on 13.
Those who will vote are, according to a YouGov poll of 8,021 people in eight major countries, particularly concerned about immigration and climate change.
Immigration into Europe has fallen markedly from a high in the midst of the 2015 refugee crisis, but Europe has yet to agree on a reform of asylum policy.
Memories and images of thousands of mainly-Muslim refugees walking through Hungary and its neighbours are still a potent tool for populists like Orban.
Far-right populists like Le Pen and Italian deputy PM Matteo Salvini hope support for their hardline stance will allow them to build a pan-European power base.
Polls suggest the far-right ENL group in Strasbourg could swell from 37 to 62 members, according to a poll of polls released by the European Parliament itself.
If the centre-right European People's Party (EPP) lose s ground or fully splits with Orban's Fidesz, the hard right could find itself in a much stronger position.
On some votes they could be joined by the anti-system Italian 5 Star movement, Farage's Brexit Party and the mainly Polish, Danish and Czech eurosceptic ECR.
"Currently, around 25 per cent of the parliament is eurosceptic and that could rise to 35," Jean-Dominique Giuliani of the Robert Schuman Foundation told AFP.
"It won't be a blocking minority, but it could have a fall-out effect, influencing the mood of other right-wing and extreme left parties," he said.
As befits nationalist groups, however, the various countries' populist parties are often starkly divided on other issues beyond immigration.
Polish and Baltic right-wingers, for example, are staunchly opposed to Vladimir Putin's Russia, whereas Moscow has friends in Hungary and Austria.
The latest polls suggest that the mainstream conservative EPP and socialist S&D, which currently form an effective majority, could lose 37 seats each.
This would oblige them to seek ties with liberals, Greens and centrists to share out Commission jobs and pass the next five-years' worth of EU legislation.
The Greens, especially in Belgium and Germany, will go to the polls motivated and buoyed by the current global wave of youth-led climate change protests.
But the arrival of Macron's new French centrist party will give the ALDE liberal grouping hope of breaking into the traditional left-right duopoly.
"There's a good chance that there will have to be at least three groups to form a working majority, a real novelty in the parliament," Giuliani said.
This game of coalitions will be important in choosing a successor to EU Commission chief Jean-Claude Juncker, and talks begin almost as soon as votes are counted.