At the headquarters of her National Front (FN) party in Nanterre outside Paris, officials believe the same forces that led to the Brexit vote in Britain and Donald Trump's victory in the United States could carry Le Pen to power.
Even some of her rivals concede a victory for the far-right firebrand is possible.
"I think Madame Le Pen could be elected," former conservative prime minister Jean-Pierre Raffarin said this month.
Pollsters now note that although Le Pen is not currently forecast to win the all-important second round showdown on May 7th, she has whittled down the projected gap between herself and her main challengers.
While it still remains unlikely that Le Pen will win the keys to the Elysée Palace in May, no one now dares rule out the possibility.
“Six months ago the possibility of her winning was zero,” Bruno Cautres, French political analyst from the Cevipof think tank told The Local. “But today we cannot say that," he added.
For Cautres the presiential election is ideal for Le Pen because personality matters much more than party or name for that matter and Marine, which is why Marine dropped all mention of Front National or Le Pen in her campaign ads.
So what are the scenarios that could lead to the once unthinkable becoming reality?
“More scandals,” says Cautres.
It's clear that while the French public might have been fairly forgiving towards political scandals in the past, they are far less tolerant of politicians' wayward behaviour now.
As we know already, Fillon's popularity has been severely hit by the Penelopegate scandal that saw his wife paid hundreds of thousands of euros to be his parliamentary assistant, where it is alleged she didn't really do much to earn the vast sums of money.
“If other candidates like Emmanuel Macron or the Socialist Benoit Hamon are hit by scandal it will play into Le Pen's hands,” said Cautres.
Of course Le Pen is also caught up in an expenses scandal and faces accusations she has misused European Parliament funds. Yet unlike Fillon, who once led the race, the allegations have not damaged her support.
“Le Pen just argues it's all part of a conspiracy against the party,” said Cautres, and her voters appear to take her side.
The other scenario that will play into Le Pen's hands is if the questions of security and identity are thrown back to the top of the agenda by more rioting in the suburbs, or if France is targeted by another terrorist attack.
It's no coincidence that Le Pen's recent rise in the polls came during the violence that broke out in several suburbs of Paris following the alleged police rape of a youth worker named Théo.
Le Pen and her party also saw a similar jump in the polls following the Paris terror attacks of November 2015.
She has proved more than any other candidate that she can capitalize on French people's concerns about radical Islam, migration, border controls and national security.
“People vote on what is most important to them at the time of the ballot,” Nonna Mayer, a political scientist and a specialist on the far right from Sciences Po, told The Local.
This is something a terrorist group like Isis may seek to exploit in the same way the Madrid 2003 terrorist attack was seen as helping influence the outcome of Spain's national election just three days later.
“We can imagine the terrorists would try to create a climate of insecurity to destabilize the population,” said Cautres.
And what about the Russians?
Macron's own team have reacted angrily recently to what they say are attempts by Russia to scupper their candidate's chances of victory in the same way they were accused of undermining Hilary Clinton's campaign to boost the chances of Donald Trump.
Both Fillon and Le Pen are seen as pro-Putin candidates. But if Fillon's standing continues to fall there are fears Moscow will step up its smear campaign against Macron, who appears to be the National Front leader's most likely second round candidate.
So whether it's unexpected scandals, violence in the suburbs, terrorist attacks, or meddling from Moscow, Bruno Jeanbart, from polling agency Opinion Way, told The Local the 2017 presidential election in France appears to be more “at the mercy of outside events” than previous elections.
(Police patrol a suburb in Paris after riots. AFP)
Preferred second round opponent
Even without any ‘outside event' influencing the election result, there are varying views on which of Le Pen's likely second round opponents would give her the best chance of victory.
On the one hand, some experts believe the 39-year-old former banker Macron would be her most favoured opponent.
Jerome Sainte-Marie of Polling Vox told AFP: "Against Macron, she has a chance of winning." And Opinion Way's Jeanbart says Fillon would be a far tougher candidate for Le Pen because the Catholic and social conservative Republicains candidate would garner a section of Le Pen's core vote.
“If she's against Macron or Hamon, Le Pen has a better chance of pulling in the vote from the right,” says Jeanbart, who adds that if Fillon's voters feel aggrieved that their candidate lost due to the scandal then there is a chance those votes will go to Le Pen.
Even Macron's supporters admit that it's difficult for the smartly-suited philosophy graduate to appeal to those living in the deprived suburbs.
“They tell us 'We will no longer block Le Pen if it means continuing on with politics as usual for another 15 years.'” Mehdi Guillo, a 23-year-old Macron campaigner told AFP. "They're tempted to let the wolf into the coop," he said.
(Pro-Europe Macron in the middle of pro-Russia Le Pen and Fillon. AFP)
Macron has tried to appeal to working class voters, campaigning on a promise of boosting their spending power and cutting their tax bills as well as fighting against unemployment.
He will have to hope that if he makes it to the second round against Le Pen, it is the economy, an area she is considered weak on, that is the top concern of the French public and not security and immigration.
And what if Fillon is Le Pen's opponent?
Cevipof's Cautres believes Le Pen would actually stand a better chance in the second round against the scandal-hit conservative.
He believes the usual “front republicain”, a term used to describe the coming together of left and right voters to vote for the candidate who is standing against the National Front, will be harder to mobilize if Fillon is Le Pen's opponent.
“It will be difficult for Fillon to incarnate the Republican Front,” he said.
Cautres believes Le Pen has a better chance of mobilizing the working classes who will be put off not just by the fake jobs scandal but also by Thatcherite Fillon's plan to implement harsh austerity including €100 billion of cuts and the shedding of half a million public sector jobs.
It may just be that many on the left decide they cannot bring themselves to even vote at all if it's a choice between Fillon and Le Pen, in the same way many American voters decided they could not back Clinton.
The same could be said if the leftist Benoit Hamon makes it to the second round, with those on the right who aren't tempted by Le Pen simply preferring to stay at home on election day rather than vote for a candidate who wants to bring in universal basic income.
Any sign of voter apathy towards mainstream candidates will have Le Pen rubbing her hands with glee as voter turnout is seen as favouring the far right candidate.
But making predictions in a highly unpredictable election race still appears futile, with a little less than two months to go.
The National Front's defeat in the second round of the regional elections in December 2015, despite strong first round results, just weeks after the devastating Paris terror attacks, shows that while she is knocking the door of the Elysée, the chances of her getting in are still low.
"As things stand, where are the votes necessary to move up from 25 percent or even 30 percent to 50 percent?," said researcher Joel Gombin, a specialist on the FN, who believes Le Pen is still some way short of victory.
But two months is a long time in French politics.