The French election is seen as a potential game-changer for the European Union.
If France turns left, as opinion polls indicate, the near-monopoly of the centre-right European People's Party in Europe would be broken.
In case of another mandate for French President Nicolas Sarkozy, Europe could move faster towards a two-speed Union and a revamp of the bloc's Schengen area that could see Greece excluded from the passport-free travel and further EU enlargement frozen.
As part of a series, EurActiv France has produced profiles of all major candidates and analysed their stances on European issues (order of appearance reflects latest opinion poll ratings):
- François Hollande: Towards a European 'New Deal'?
- Nicolas Sarkozy: A very French European
- Marine Le Pen: What she means for Europe
- Jean-Luc Mélenchon: For a European revolution
- François Bayrou: A tamer federalism for Europe
Early results from exit polls are expected as early as 18:00, both for the first round and the 6 May run-off.
But because French media are prohibited from making any announcement before 20:00, millions of French people are expected to zap, tune in or log into foreign French-language news media in Belgium and Switzerland, which are not bound by such constraints.
According to opinion polls, the conservative incumbent Sarkozy and Socialist candidate François Hollande have the biggest chances of making to the 6 May run-off.
Both are running neck-and-neck for the first round, with 27-28% of the votes each, the latest opinion polls show.
However, two other contenders have emerged as a potential "third man".
Far-right candidate Marine Le Pen is credited with 16.5% of voting intentions and has been on the rise in recent days. On the other extreme of the political spectrum is Jean-Luc Mélenchon, who appears likely to become the biggest revelation of this election.
Mélenchon's flamboyant anti-capitalist rhetoric has won him the reputation of "a new Robespierre" in the French political media. He is credited with 14% of voting intentions, but his electorate appears very motivated and surprises may occur, especially if turnout is low.
The centre – and the rest
François Bayrou is the only centrist but according to analysts, his declining ratings, around 10%, appear to indicate that the political centre is not fashionable in France these days.
The remaining five candidates are unlikely to make a big difference.
Eva Joly, a Norwegian-born magistrate running for the Green party, is credited with only 2.5% of voting intentions, despite the party's good score at the 2009 European elections, with 16.28% of votes.
On the extreme left are Nathalie Arthaud from Lutte Ouvrière, a French Trotskist party, and Philippe Poutou from the New Anti-capitalist Party. Nicolas Dupont-Aignan is a sovereignist and Jacques Cheminade is a maverick politician running for president for the second time, after having scored 0.27% in 1995.