He said perhaps the main reasons the RN had become more palatable was the state of the other parties, which were either in ruins or had radicalised, making the Le Pen camp appear more mainstream.

“First, we have a president who wanted to play poker and lost, never had a real political party to act as a conveyor belt for his ideas and is now paying for the fact that he wanted to establish a quasi-vertical link with the French people and failed,” he told the Telegraph.

“Second, France is probably the only major country in Europe without a conservative Right.”

The once-mighty Gaullist Republicans, which won 10 per cent of the vote, are deeply divided after a spectacular split over whether ot not to back Ms Le Pen.

Ms Le Pen has benefited from the xenophobic, anti-Islamic outbursts of Eric Zemmour, a polemist whose rhetoric makes her look like a shrinking violet, and has distanced herself from Germany’s far-Right AfD.

Last month, she said her party would no longer sit in the EU parliament with the AfD after the head of its European election list said that someone who had been a member of the SS was “not automatically a criminal”.

By contrast, she has sought to build bridges with Giorgia Melona, the Italian prime minister, who on Monday said that attempts to “demonise” far-Right voters were losing impact.

“I notice something that in different forms is also happening in Italy: the constant attempt to demonise and corner the people who don’t vote for the Left,” said the most Right-wing Italian leader since the Second World War.

“It’s a trick that serves to escape debating on the merits of different political proposals. But it’s a trick that fewer and fewer people fall for. We’ve seen it in Italy, and we’re seeing it more and more in Europe and throughout the West”.

But above all, said Mr Camus, Ms Le Pen’s ranks had swollen due to the mass rejection of the fiery Jean-Luc Mélenchon, an admirer of Hugo Chavez and Mao Zedong, whose Unbowed France, LFI, is part of the New Popular Front, which came second on Sunday.

“No doubt on Sunday, moderate voters, even social democrat voters, will find it very difficult to put a Popular Front ballot paper in the box due to his outbursts.”

This explains why Mr Bardella is so keen to debate with Mr Mélenchon rather than a more moderate member of the Left-wing alliance.

Beyond his tepid support for Ukraine and refusal to call Hamas a terrorist organisation after the Oct 7 attack on Israel, Mr Mélenchon has been accused of downplaying anti-Semitic incidents and pandering to the radical Muslim vote.

“It reminds me a lot of George Galloway in the UK whose Respect Party tried to bring about this sort of fusion between political Islam and the far Left. It worked quite well but is a turn-off for most,” he said.

As parties jockey to forge alliances and strategies to keep the RN out, Sunday will be the ultimate crash test of whether the de-demonisation drive is complete.

Supporters upbeat

Meanwhile, its supporters have the wind in their sails and are prepared to forget Mr Bardella’s decision to dilute some of his policies.

Shortly after the results were announced at Ms Le Pen’s northern fiefdom of Hénin-Beaumont, one said: “He’s reasonable, in fact he does what other parties fail to do, which is not to offer promises he cannot keep. We won’t be able to do everything straight away.”

Then the subject moved onto immigration and the tone became more radical.

One supporter called Vanessa said: “We need to bin immigration. We don’t have the same culture, we don’t have the same values. They want to try and change us. Never. I’d rather die. With the Popular Front, we’ll end up under under Sharia law. No way.”

Edouard was even more direct. “I’ve had enough of the Left that doles out lessons to everyone. If they love migrants that much, they can have them in their block of flats. They have houses, a job and cars. Why are they in my social housing and whites sleep on the sidewalk?”

Minutes earlier, Ms Le Pen had taken to the stage to call on the French to vote National Rally to “finally get back unity and fraternity”.