Voting started in mainland France on Sunday in an election that could make Nicolas Sarkozy the 11th European leader to be swept from office by the economic crisis and crown Francois Hollande as France's first Socialist president in 17 years.
Buoyed by a tide of anger over Sarkozy's inability to rein in rampant unemployment during his five-year term, Hollande was between four and eight points ahead in final opinion polls for a vote that could mean a shift in direction for Europe.
Despite shaving a couple of points off Hollande's lead in the last days of a frenetic campaign, the conservative's own aides privately admitted it would require a miracle for him to turn the odds in his favour and clinch a second term.
"He's like a runner - he won't consider it's over until the very end, but I'd say he has one chance in six," a member of Sarkozy's inner circle told Reuters on condition of anonymity shortly before campaigning drew to a halt on Friday.
"Uncertainty about the outcome of the vote has fallen to an extremely low level," said BNP Paribas economist Dominique Barbet.
Polling stations are open from 7 a.m. British Time (0600 GMT) to 5 p.m. EDT (1600 GMT) on Sunday, and two hours later in big cities.
Reliable projections of the result based on a partial vote count will be published as soon as the last polling stations close. Media that publish exit polls or partial results before that risk fines and legal action.
Hollande, a mild-mannered and popular career politician, has held a steady lead for weeks after outlining a comprehensive programme in January based on raising taxes, especially on high earners, to finance spending and keep the public deficit capped.
As much as his own programme, he is benefiting from a tide of anti-Sarkozy sentiment due in part to the incumbent's showy and occasionally arrogant personal style and in part to anger over the same economic gloom that has felled leaders from Britain to Portugal.
The vote coincides with a Greek election where voters are also expected to punish major parties for economic misery.
"Clearly the voting public is getting fed up with failed policies," Nobel Prize-winning economist Paul Krugman told Reuters TV in New York.
Sarkozy, sometimes called the hare in the race and his rival the tortoise, launched his campaign late and unveiled proposals one by one in high-energy speeches that swerved hard to the right as he sought to win back low-income voters that polls show have ditched him for either the radical left or extreme right.
His aggressive rallies and pledges to rein in immigrant numbers, hold policy referendums, crack down on tax exiles and make the unemployed retrain as a condition of getting benefits did not reduce Hollande's lead. He surprised many by failing to land a knockout punch on his rival in a televised debate.
In two further blows in the last days of the race, both far-right leader Marine Le Pen, who came third in an April first-round vote with 17.9 percent, and centrist Francois Bayrou, who came fifth with 9.1 percent, refused to endorse Sarkozy.
While Sarkozy spent Saturday in the privacy of his home in Paris with former supermodel wife Carla Bruni, Hollande and his journalist partner Valerie Trierweiler were out shaking hands with supporters, signing autographs and sampling cheese and strawberries in rural France.
The election comes at a crucial time for the convalescent euro zone, as France, Europe's No. 2 economy, is a vital partner for Berlin in safeguarding the single currency bloc's future.
If Hollande is elected, joining a small minority of left-wing governments in Europe, he wants to challenge Berlin's focus on austerity policies with a demand for pro-growth elements to be tacked on to the euro zone's budget responsibility pact.
The Socialist plans to visit centre-right Chancellor Angela Merkel within days of the election to discuss his ideas.
German relations aside, France is grappling with feeble growth and 10 percent unemployment, a gaping trade deficit and over-high state spending that is straining public finances and was a factor in Standard & Poor's cutting of its triple-A credit rating.
While financial markets are coming around to Hollande's pro-growth ideas, given growing support for them elsewhere in Europe, Hollande would need to reassure them quickly about his economic plans as fears resurface over the euro zone's debt woes.
While economists want him to trim over-optimistic official growth forecasts and compensate for that with spending cuts, political analysts fear that would be difficult with no mandate and with left-wing voters hoping instead that he will raise the minimum wage and reverse a recent sales-tax hike.
French 10-year bond yields fell to 2.87 percent on Friday, a level not seen since early October, as initial jitters over a Hollande victory abated.
Yet French debt would remain vulnerable to selling pressure if he wins, as markets and credit rating agencies wait to be convinced of his fiscal credentials.
Little known outside France, Hollande would also have his diplomatic skills put to the test fast if he wins, with a Chicago NATO summit looming in late May and a Group of 20 summit in Mexico in late June.