The French presidential election will be decided between centrist Emmanuel Macron and far-right leader Marine Le Pen.
Macron - centrist candidate and former protege of François Hollande - beat Le Pen on Sunday, becoming the bookies' favourite to become French President.
Only about one-third of those who voted Fillon will be tempted to vote for Marine Le Pen in the second round. The rest will vote Macron or abstain
Edouard Lecerf, Kantar
But candidates are pitted against each other twice in the French presidential election. The first round is now over, and as the top two candidates with the highest vote share in the first round, Le Pen and Macron will now face off in a second-round run-off on May 7.
Macron is still widely expected to be able to build a broader voting base than anti-establishment Marine Le Pen. This is due to the fact that many of the first-round supporters of conservative François Fillon and far-left Jean-Luc Mélenchon, who collectively attracted 39.5 per cent of the vote, are expected to now switch to Macron.
According to recent polling, Macron looks set to attract the majority of these voters, helping him to beat Le Pen by a margin of around 30 points.
Experts say that a good turnout and a convincing win for Macron in the first round leaves Le Pen with a mountain to climb to beat him.
Edouard Lecerf of the Kantar Public polling firm told The Telegraph: "Macron’s strength is that even if he isn’t the first choice for the 50 per cent of the first-round voters whose preferred candidates were eliminated in the first round, he is still seen as acceptable by many of them, whereas Marine Le Pen isn’t."
Where will other candidates' voters go?
While Macron and Le Pen have grabbed the headlines by progressing through to the second round, it is important to remember that less than half of French voters backed these two candidates.
Macron attracted 23.8 per cent of the vote while Le Pen scooped up 21.4 per cent. This leaves around 55 per cent of the people who voted in round one without their preferred candidate in the run-off.
This figure hasn't been above 50 per cent since 2002 when Jacques Chirac and Jean-Marie Le Pen were the top two candidates in the first round, pulling in just 36.7 per cent of the vote between them.
It means that the result of the second round of this year's contest will be decided upon which way the 55 per cent whose candidate didn't make it through choose to vote on May 7.
Polling conducted by Ifop at the end of last week suggests that Macron - a centrist - should benefit from this landscape. He should be able to attract a wider spectrum of voters compared to Le Pen, pulling in left-leaning voters from Hamon and Mélenchon as well as those leaning to the right that voted Fillon in the first round.
Francois Fillon came third in Sunday's first round with 19.9 per cent of the vote and pledged his support to Macron in his concession speech. The Ifop poll suggests that 42 per cent of Fillon supporters will heed their candidate's advice but that 31 per cent would switch to Le Pen.
While 51 per cent of Mélenchon supporters said that they would switch to Macron in round two, just 12 per cent said they'd vote for Le Pen with the remaining 37 per cent preferring to abstain. The far-left candidate has refused to endorse Macron, leaving a small opportunity for the Front National to scoop up some of the Eurosceptic far-left.
All this means that Le Pen has a lot of persuading to do in the next fortnight if she wants to persuade enough voters to change their minds and back her bid.
Could Le Pen win?
Both the pollsters and the bookmakers think that it's very unlikely that Marine Le Pen can beat Emmanuel Macron in the second round of the presidential election.
But pollsters and bookmakers have been wrong quite a lot recently, and this run-off is unprecedented due to the lack of establishment candidates on offer.
Macron's party, En Marche! is a brand new offering which has so far captured the imagination of voters. But, with no history behind it, it's hard to tell how flaky this support could be.
It's also unclear how - in the event of victory - Macron could rule France effectively given he currently has no representatives in the National Assembly or the Senate.
High abstention rates could benefit the far-right leader
Some have predicted high abstention rates in the French election - which could help Marine Le Pen.
In contrast to the supporters of Macron, polls show that those who say they will vote for Le Pen are most certain of their vote. This means that levels high of uncertainty and apathy could benefit the far-right leader.
Macron will rely on those that voted for Fillon, Mélenchon and Hamon in the first round - but 37 per cent of Mélenchon voters, for example, have said that they'll abstain in the second round.
So even though Le Pen win is very unlikely to win, her team will hope that she could have a small chance if Macron fails to inspire his voters to turn out.
Experts, however, say this is unlikely - with no sign of low turnout or a surge for Le Pen.
Kantar's Mr Lecerf said Ms Le Pen would have had more chance of victory in the final round if there had been a low turnout in the first. "That would left a reserve of voters whom she could mobilise for the second round but it didn’t happen as the first-round turnout was high, at nearly 80 per cent."
He added that if she had come top in the first round, that could have encouraged more voters to back her, but she came second.
A victory for Ms Le Pen would be more likely if she faced "a polarising candidate" in the final round, such as the scandal-tainted Mr Fillon, or the communist-backed Mr Mélenchon.
"Only about one-third of those who voted for Fillon will be tempted to vote for Marine Le Pen in the second round. The rest will vote for Macron or abstain," Mr Lecerf said.