Two main candidates, the conservative former minister Nicolas Sarkozy, and the Socialist former minister Segolene Royal, have remained steady as the voters' most popular choice to go forward into the decisive second round after today's first round narrows the field.

But experienced French pollsters and commentators point out that given the high number of undecided voters on the eve of the election . . . roughly one third of the 44m strong electorate . . . there could still be a big surprise that could catapult one of the other two candidates into the second round. On the eve of the election, with the polls pointing in different directions, the first round is too close to call.

Francois Bayrou, a centrist former education minister campaigning for an end to the left/right divide that has traditionally polarised French political life, and the farright leader Jean-Marie Le Pen are the jokers in the pack who have created a sense of suspense about the outcome.

The only thing on which the opinion polls agree is the pecking order of the candidates' popularity. Sarkozy, President Chirac's former hardline interior minister, has consistently been in first place, with Royal, who was a minister under Francois Mitterrand, always in second place. Bayrou and Le Pen come in third and fourth, according to the polls.

But yesterday's opinion polls produced different results for each candidate, with Sarkozy oscillating between 28% and 30%, and Royal coming in with 23-24%. Bayrou recorded 18-19.5%, while Le Pen came in with 13-14%.

If the polls are reliable . . . and in the last presidential elections they were not . . . that should mean that the second round would be a traditional battle between the right and the left. That is how Royal and Sarkozy have framed the debate.

But polling experts say that Le Pen's vote is likely to be underestimated . . . as it was in 2002 when he shocked the country by securing a place in the run-off against Chirac.

Equally, Le Pen could drain voters from the score of Sarkozy, who could suffer from an "anti-Sarkozy" campaign focusing on his divisive personality.

Royal could meanwhile be vulnerable if voters decided to switch to the centrist candidate Bayrou, who could benefit from an "anti-system" protest vote.

Brice Teinturier of the polling agency Sofres told Le Monde: "we cannot rule out a reversal of the curves" of Royal and Bayrou, putting the socialist candidate in danger.

However Socialist party managers remain confident that their candidate stands to benefit from an expected high turnout as the French consider the stakes in voting for a president from a new generation who will turn the page on 12 years of economic decline under President Jacques Chirac.

They sense that unlike the 2002 poll, voters will shun the extreme positions incarnated by Le Pen in favour of a clear "choice of society" as offered by Sarkozy on the right and Royal on the left.

"It is a vote for change. People know we can't carry on like this, " said a member of Royal's campaign team, the "Blairite" senator Jean-Marie Bockel. "But they are afraid of being the victims themselves."

On the final day of the campaign, Royal strolled round a Paris market where she tasted a strawberry.

HOW THE ELECTION WORKS

44,000,000 registered voters will decide France's next president, who will serve for five years.

About 82 areas, including Brest, Le Havre and several towns in greater Paris, are experimenting once again this year with electronic voting machines.

The projected result will be announced on French television at 8pm local time (7pm in Ireland) based on early returns from selected areas.

The first two candidates go forward to a run-off in the second round on 6 May.

The presidential election will be followed almost immediately by parliamentary elections, once again over two rounds, on June 10 and 17.