At the foot of the bronze statue of an armour-clad Joan of Arc, outside the Front National headquarters on the outskirts of Paris, someone had laid two wreaths of perfect white lilies to mark the 600th anniversary of the martyr's birth.

The French far right has long claimed the peasant girl who became the scourge of the English as its symbol, rebuffing recent attempts by Nicolas Sarkozy's ruling UMP party to wrest her from them.

Today, six centuries on and exactly three months from France's presidential election, Joan's legend has never seemed so relevant to backers of the FN's charismatic leader, Marine Le Pen. Once again, France must free itself from unwelcome foreign intervention and national pride must be restored. Is this Le Pen's moment?

The conjunction of the eurozone crisis, the loss of France's triple-A credit rating, and rampant unemployment, currently at a 12-year high, has given unexpected credibility to Le Pen's anti-Europe, anti-immigration stance. The economic storm has created what political pundits and pollsters believe may be a now-or-never moment for the Front National after 40 years spent largely in the political backwaters.

Poll after poll places Le Pen third with 21.5%, hovering just behind Sarkozy at 23.5%, and with the Socialist party's François Hollande well in the lead for the first round of the presidential vote in April. If the opinion polls are accurate, it is perfectly feasible, allowing for the accepted margin of error, for Le Pen to reach the second-round run-off a fortnight later. Some surveys show support for the FN candidate to be considerably higher, topping 30%.

The days when the FN, then run by Le Pen's father, Jean-Marie, now 83, could be dismissed as the loony fringe of French politics have long gone. Some of its policies have been anxiously emulated by Sarkozy's government as it shifts to the right, giving them a mainstream respectability.

Left Bank intellectuals, the luminaries of Paris's beau monde and members of the capital's chattering classes tend to crumple with a mixture of fear and loathing at the mention of Le Pen's name. In the gritty post-industrial areas of France, however, where families are struggling daily with the sharp end of the economic crisis – job losses, factory closures, rising food prices – Le Pen's message of patriotism, protectionism and state paternalism, wrapped up in what passes for common sense, falls on receptive ears.

Le Monde has described her economic programme as "unreal figures and a real threat", but she insists that her message is aimed at "ordinary French citizens". It is, at its most simplistic, that France must regain its former glory; it must reindustrialise to make things and create jobs; it must dump the euro and throw up barriers against immigration, cheap imports and external interference; France must come first. The campaign slogan is simply Marine Le Pen: Voice of the People, Spirit of France.

"I speak for the values of the people. I don't have to pretend to be one of them, I am," she told me in a recent interview. "My father was the son of a fisherman, my mother the daughter of a small businessman. That's the background I come from: where there is respect for the values of honesty, hard work, merit, patriotism, a sense of sacrifice, liberty, respect and discipline."

At the party headquarters, an uninspired architectural shoebox in La rue des Suisses in the Paris suburb of Nanterre, visitors are greeted with a computer screen relaying images of Marine Le Pen, 43, on stage, at rallies, on the campaign trail.

She is physically impressive; tall, strapping, a "big, healthy, blonde girl... an ideal physical specimen", as her father once described the youngest of his three daughters.

Asked if he is excited by the unprecedented poll ratings, the FN party treasurer, Jean-Michel Dubois, refuses to be drawn. "I have been in the party since 1986," he replies. "I am pragmatic." When pressed, he says: "Everyone knows Marine Le Pen will be in the second round." Dubois claims that the economic crisis has proved something extremely important: "What Marine Le Pen warned, what she said would happen, was right. Everyone now realises she was right. "

The French political elite was given a short, sharp lesson in not underestimating the FN in 2002. In a completely unexpected scenario, Jean-Marie Le Pen knocked the Socialist candidate out. He lost in the second-round run-off, but the incident provoked a bout of national shame and self-loathing that left deep scars.

Jean-Marie Le Pen's hectoring antisemitism and bullying rhetoric could not sustain the success. But in January 2010 Marine Le Pen was elected the FN's president and overhauled the party.

She dumped the shaven-haired bully boys nominally responsible for "security" at FN rallies for fresh-faced girls in jeans and crisp T-shirts, and abandoned the neo-Nazism and outdated references to the second world war. She even voiced support for homosexual marriage.

There were flashes of Le Pen senior in her railing against Muslims praying in the streets – which she likened to the Nazi occupation – "corrupt" politicians, European technocrats, and that old FN chestnut, immigration. And while it was generally agreed that she was softer and cleverer than her father, the fundamental ideology of the FN seemed to have changed little.

"She's a young woman and she plays on that softer image. She's also good at getting her message across, much, much better than her father," said Nonna Mayer, who is an expert on France's far right and a professor at the Paris Institute for Political Studies (Sciences Po).

"But it's the same politics of scapegoating that it always has been. It's still the extreme right. There's no getting away from it."

Veteran political commentator Alain Duhamel branded Le Pen "just as big a peril" as her father, but Jérôme Fourquet, of the pollster company Ifop, attributes her popularity to the parlous state of the global economy, which he says gives her views "credibility". "The evolution of this economic crisis will be very important to the Front National. If it gets worse, she could profit from the situation," he said.

Marine Le Pen has admitted struggling to amass the 500 signatures of support from French mayors needed to run for president, but says that it would be "scandalous" if she were excluded. She certainly believes her moment has come.

"The tectonic plates are shifting," she says.