An Opinionway poll placed Mr Macron on 26 per cent in round one, with Ms Le Pen on 22 per cent and her nearest challenger, Leftist Jean-Luc Mélenchon, gaining ground on 17 per cent.

Mr Macron would go on to win the runoff with 53 per cent of the vote but, accounting for the “margin of error”, it could go either way, said her team.

One lone Atlas Politico survey on Thursday night even predicted Ms Le Pen could actually clinch the election by a half-percentage point – though this has not been repeated elsewhere.

Abstention is Marine Le Pen’s biggest concern

However, the party’s biggest fear is abstention, as polls suggest her younger, less-educated and less well off supporters are more likely to stay away than those behind Mr Macron.

Presidential elections have traditionally enjoyed high voter turnout, but abstention has been rising. The Ipsos pollster forecast that as much as a third of voters may sit out Sunday’s election. That would set a record and exceed the number voting for any candidate.

Mr Macron, likewise, has warned of a Brexit-style upset unless his supporters go to the polling booths.

Ms Le Pen’s concerted effort to soften her image and place her usual bugbears of Europe and immigration on the back burner appears to be finally paying off.

But on Thursday, she also hit those old buttons, while warning the election was a decisive clash between “nationalists and globalists”.

She received huge cheers for promising to inscribe “national preference” for French in housing and employment in the French constitution, which received chants of: “We’re in our own home.”

Earlier, the anti-immigration politician vowed to ban the Muslim headscarf in all public spaces, saying it would be enforced by police in the same way as seatbelt-wearing in cars.