Opinion polls have suggested for months that the incumbent president, Nicolas Sarkozy, and his Socialist challenger, François Hollande, will probably emerge as the finalists in a field of 10 candidates. The two would then face a run-off on May 6.
But the polls also found significant numbers of undecided voters among the 44.5 million registered and that up to 25 percent of all voters may abstain.
Under a gray sky and amid intermittent showers, many voters in Paris expressed the sense of deep ambivalence that had been reflected in opinion surveys in the months leading up to Sunday’s contest. Neither of the two front-runners has managed to rally significant support behind his party or his program, setting the stage for what is expected to be a stronger-than-usual result for fringe parties on the left and on the right of the French spectrum.
Mr. Hollande, 57, has sought to present  himself as a ”normal” candidate in contrast to the brusque, ”hyper-presidency” of Mr. Sarkozy, also 57. But while Mr. Sarkozy  has seen his popularity sink, along with the economy, to record lows for a French leader, his main rival has run a timid campaign that presents few major new initiatives.
”Everyone is voting but no one is excited," said Hervé Thiery, 59, a flea market vendor on the avenue de Flandre in Paris’s working-class 19th arrondissement.
John Hustaix, a 24-year-old student, said he had wanted to abstain but voted reluctantly for Mr. Sarkozy, largely out of concern that uncertainty about the consequences of a Hollande victory might spark financial market turmoil.
”Nobody knows exactly what’s going to happen whoever is elected,” Mr. Hustaix said. ”Hollande is not going to be able to enforce his program, and Sarkozy didn’t disclose specifics on what he is going to do aside from immigration and security.”
At midday, Interior Ministry estimates put the early turnout at just over 28 percent, down slightly from the same point in the voting in 2007. Final voter participation five years ago was a record 84 percent.
The last polling stations are scheduled to close at 8 p.m. and the first official result estimates were expected shortly thereafter. French law bars the early publication of exit polls, although media organizations in neighboring Belgium and Switzerland were expected to publish initial results online from districts where the polls close at 6 p.m. as soon as they are available.
This year’s contest is expected to contrast sharply with elections five years ago, when three out of four French voters supported the mainstream. That campaign’s “third man” was a centrist, François Bayrou, who garnered 18 percent of first-round votes.
This time, however, many voters have become disaffected, even angry, with what they regard as the timid proposals of Mr. Sarkozy and Mr. Hollande, and have turned to the fringe parties — particularly the far-right National Front, led by Marine Le Pen, and the Front de Gauche, a hodgepodge of former Communists and anti-globalists led by Jean-Luc Mélenchon.
Together, support for Ms. Le Pen and Mr. Mélenchon could be as much as 30 percent and outstrip the votes for either Mr. Sarkozy or Mr. Hollande. Mr. Bayrou, the centrist, is polling at just 10 percent.
Most polls have margins of error of about three percentage points, and in the past they have underestimated the vote for the National Front and, in 2007, for Mr. Sarkozy. While polling is difficult with 10 candidates, the surveys agree that the race is tight.
Outside a polling station on the rue Houdon  in the 18th arrondissement,  Antoine and Fanny Dubos, a young couple with a 2-year-old daughter, were split on whom to support. Ms. Dubos, an art history student, said she voted for Mr. Hollande because  “we need a strong left right away” to defeat Mr. Sarkozy.
Mr. Dubos, an urban planner, however, voted for Mr. Mélenchon because he was skeptical that Mr. Hollande had the leadership skills to guide France through the current economic crisis.
“We are heading straight into a wall, so I say let’s give a sharp wheel turn and see what happens,” Mr. Dubos said.
The two main candidates are already looking to the second round in a couple of weeks. Mr. Sarkozy is hoping to gain some momentum by coming in first on Sunday. The traditional French understanding is that in the first round, people vote with their hearts, and in the second round, with their heads. And the second round, barring surprises, should be a classic French fight between the left and the right.
Polls have indicated that Mr. Hollande is favored to win a run-off, which is likely to bode for a change in the direction France, a pillar of the European Union, takes in addressing crucial issues, not least of which is the grinding euro crisis.
After casting his vote Sunday in his political hometown of Tulle, in central France, Mr. Hollande acknowledged as much.
“This is an election that will weigh on the future of Europe. That’s why many people are watching us,” he said. “They’re wondering not so much what the winner’s name will be, but especially what policies will follow.”
Mr. Hollande has advocated higher taxes on the rich and a greater emphasis on growth over austerity, a stance that would create strains with Germany and rattle financial markets that are already nervous about the size of France’s debt. He has also said that he wants to pull French troops out of Afghanistan sooner than NATO has agreed to do.
Steven Erlanger contributed reporting. COPY : http://www.nytimes.com/reuters/