Polls have opened in the first round of France’s most unpredictable and high-stakes presidential election in decades, with far-Right leader Marine Le Pen and the maverick centrist Emmanuel Macron leading the field.
A Le Pen victory could lead to the collapse of the European Union, experts warn, but after the victory of Donald Trump in the US and the Brexit vote in the UK, most agree that there is no safe bet in the French race.
Unprecedented security measures were in place to keep voters safe as they cast their ballots, with 50,000 police officers and 7,000 soldiers deployed across the country.
Voting began just three days after a French jihadist shot dead a policeman on the Champs-Elysées in Paris, furthering pre-election jitters and pushing security and terror back to the top of the political agenda.
Islamic State of Iraq and the Levant (Isil) claimed the attack, as it has done for a series of assaults in France that began in early 2015 and have cost the lives of more than 230 people.
At a polling station in a primary school on Rue Martel in the trendy 10th arrondissement of Paris, there were no police on duty and no security checks.
Parisians doing their civic duty there before shopping for lunch said they were undeterred by terror threats.
"I'm 85 and I lived through the war and the Nazi occupation, so I'm not scared," said Gerard Samson, a retired film-maker.
Mr Samson said he had been a life-long supporter of the Socialist party but, as the Socialist candidate Benoit Hamon has little chance of getting elected, he was conflicted.
"This is the first time I have had to hesitate," he said, declining to say who he had plumped for.
There are 11 candidates in the running for Sunday’s first round, including a pair of Trotskyists, three fringe nationalists, a former shepherd, and a man who wants to colonise Mars.
But there are just four who stand a chance of getting through to the run-off on May 7: Ms Le Pen, Mr Macron, the communist-backed firebrand Jean-Luc-Mélenchon, and the scandal-scarred conservative François Fillon.
The pair who will square off for the second round will be known at around 7pm UK time when usually accurate exit polls are announced.
One of the last opinion polls before campaigning was brought to an early halt by the killing of the policeman in Paris showed that Ms Le Pen and Mr Macron were tied on 23 per cent, with both Mr Mélenchon on 19.5 per cent and Mr Fillon on 19 per cent snapping at their heels.
But due to the margin of error pollsters factor in, any pair from those four could make it through to the second round to battle it out to replace the deeply unpopular Socialist President François Hollande, who failed to end mass unemployment or turn around the country’s ailing economy.
The uncertainty is heightened by polls showing that one in three of the 47 million registered voters remained undecided just days before the vote.
The results of the French elections are being keenly watched across the world, with many experts predicting that a victory by Ms Le Pen, 48, who says she will pull France out of the euro, could cause chaos in the financial markets and lead to the collapse of the EU.
If Ms Le Pen or Mr Mélenchon – who both rail against globalisation - make it to the run-off, this will be seen as a victory for the populist wave reflected by the votes for Donald Trump and Brexit. But if neither candidate makes it through, that would be interpreted as a clear sign that populist nationalism is finally receding.
Mr Trump weighed in to the French political debate after the Paris attack on Thursday, saying the shooting would "probably help" the anti-EU and anti-immigrant Ms Le Pen because she is "strongest on borders, and she's the strongest on what's been going on in France".
"Whoever is the toughest on radical Islamic terrorism, and whoever is the toughest at the borders, will do well in the election," he said of the candidate who said that she will hold a referendum on taking France out of the EU if the bloc doesn’t carry out radical reform.
Mr Trump’s predecessor, Barack Obama, came out for Mr Macron, telling the 39-year-old former Socialist finance minister in a phone call that he should “work hard all the way through because you never know, it might be that last day of campaigning that makes all the difference".
Jean-Marie Le Pen, Marine Le Pen’s father and founder of her Front National party, made it through to the second round of the 2002 presidential election but was then crushed by the conservative Jacques Chirac after both Left- and Right-wing voters rallied together to keep the far-Right leader out of the Elysée.
Polls predict that this will likely happen again if Ms Le Pen reaches the May 7 run-off, but this would be complicated if she were up against Mr Mélenchon, 65, whose old-school socialist agenda is anathema to many centrist and conservative voters.
Intelligence services have warned that riots could break out in cities across France after results of the first round are announced on Sunday evening.
Trouble is almost certain if the pair squaring off for the second round are Ms Le Pen and Mr Mélenchon, they said.
An intelligence report leaked to Le Parisien newspaper spoke of “public disturbances in the case of the presence [in the second round] of parties which are said to be extremist”, a reference to Ms Le Pen and Mr Mélenchon.
“In this case, protests are almost certainly to be expected,” said the document, which also warned of farmers, hospital staff and students taking to the streets to protest the results.