Backstage at a rally in southern France in the early days of the presidential race, Marine Le Pen took a puff on the electronic cigarette that has replaced her two-packets-a-day tobacco habit. “I’m going to run a joyful campaign,” she smiled.

Le Pen wanted to soften her harsh image and “soothe” voters – she had posed for pictures hugging horses and pet kittens – but also to offer a hardline programme she believed would “reassure” a French population despairing of decades of mass unemployment and a persistent terrorist threat.

The aim, as always for the far-right Front National founded by her father, Jean-Marie Le Pen, in 1972, was keeping France for the French. There would be a referendum to change the constitution so that “national priority” would be given to French people over non-nationals in jobs, housing and welfare. There would be another referendum to leave the European Union. Le Pen promised an immigration clampdown and a ban on religious symbols, including the Muslim headscarf, from all public places in France.

Marine Le Pen, 48, is the closest she has ever been to the French presidency – with a chance of making it to the final runoff in an election that is impossible to predict. In the six years since she took over the party from her father, she has steadily increased her party’s vote in every local and European election. If her ex-paratrooper, Holocaust-denying, provocateur father was content to be a protest vote, Marine Le Pen wants power and political office.

Marine Le Pen visits a horse show in Villepinte, Paris, in December. Photograph: Jacky Naegelen/Reuters

Le Pen, controlled and image-conscious, has always a walked a tight line between denouncing the system and trying to be part of it. Her life has played out in the public eye ever since, aged six, she was photographed being tucked into her bed in a bedroom incongruously wallpapered with Front National election posters about fighting the “Marxist cancer”. The Le Pen family dynasty was always something of a national soap opera, with the blond clan living together – including the three Le Pen daughters well into their 30s – in a 19th-century manor house perched on a hill outside Paris, watched over by dobermans.

But the troubled father-daughter bond – and the brutal public breaking of it – has hung over her presidential campaign. Marine Le Pen’s election strategy has been to broaden her voter base by sanitising the party’s image, moving it away from the racist, jackbooted and antisemitic imagery of the past. The problem was that Papa Le Pen felt left out. In 2015, he deliberately wrecked her plans by repeating the Holocaust denials that had landed him a series of convictions for hate speech and contesting crimes against humanity. After a bitter public feud, she expelled him from the party. He publicly disowned her and they haven’t spoken since.

But the ghosts of the second world war persist in French politics. Marine Le Pen was asked on a radio programme this week about a major wartime roundup of Jews in Paris. She said France as a nation was not responsible, only “those who were in power at the time”, sparking fury from Jewish organisations. Le Pen argued that modern France should not be locked in permanent repentance and that the “real” France was Gen de Gaulle’s resistance, not the “illegal” Nazi-collaborationist Vichy regime. “If you’re trying to say Marine Le Pen is a Nazi, come out and say it but that will make everyone laugh to the rafters because it’s simply not credible,” her chief strategist, Florian Philippot, angrily told a chatshow host. Le Pen slammed what she called a pointless controversy.

Marion Anne Perrene Le Pen – swiftly nicknamed Marine – was born west of Paris in 1968, the youngest of three daughters. Her father showed off his children in the press. But their home life was more disjointed than it seemed. In the Le Pens’ first Paris apartment building, the children lived separately from their parents, in a flat upstairs with a nanny. Jean-Marie Le Pen and his wife, Pierrette Lalanne, would go off on holiday or long sailing trips around the world on their own, sometimes missing Christmas.

Marine Le Pen attending a wreath-laying ceremony in 2010 with her father Jean-Marie at the statue of Joan of Arc in Paris. Photograph: Jacques Brinon/AP

It was only when the eight-year-old Marine woke up in her nightdress amid shards of glass and a blown-away bedroom wall, after a bomb attack aimed at killing her father, that she realised his political role and the extent of hatred towards him. “As an eight-year-old girl, I was suddenly made aware of death,” she told me when she took over the Front National leadership. “But maybe that gave me a distance, a kind of armour, that’s useful when you’re aiming for positions of responsibility.”

The family surname was a burden – she recalled teachers at school referring to her sisters as “daughters of a fascist” – but she constantly stood up for her father. When, in 1985, the paper Libération revealed that Le Pen Sr had engaged in torture during the Algerian war, he denied it and advised the teenaged Marine Le Pen to take the day off school. She refused and went in defending him.

In the 1980s, as he gained political prominence, Le Pen Sr commissioned a biography from a journalist who spent time at the family’s manor house. One day, Marine , then 16, was surprised to find one of her older sisters waiting outside school. “Mum’s gone,” she said. Without telling anyone, Lalanne had taken all her possessions and left with Le Pen’s biographer to set up a new life. She didn’t see or speak to her daughters for more than 15 years. Marine , the youngest and most attached to her mother, was left alone with her distant and distracted father. She said she waited every day for some kind contact from her mother, but none came.

“Marine Le Pen grew up in a very odd atmosphere, a family that appeared close but was actually very distant,” said David Doucet, who co-authored a biography of her early years, La Politique Malgré Elle. “She lived almost 20 years without her mother. Her father hardly knew her. She was brought up by nannies and governesses, left to her own devices.”

Jean-Marie Le Pen with his wife Jany and daughters Marine and Yann in 2002. Photograph: Prestige/Getty Images

A vicious, public divorce battle followed. Jean-Marie Le Pen rebuffed Lalanne’s maintenance claims, saying she should work as a cleaner. As revenge, Lalanne posed naked in French Playboy scrubbing kitchen floors.

Marine Le Pen occasionally accompanied her father out campaigning as a teenager as a way to spend time with him and win a little attention. But she didn’t initially set herself up for a political career. She told me once: “My father says I’m like Obelix. I fell into the magic potion of politics when I was young.” In fact, she had tried to escape the party by studying law. To make extra income beyond her law firm jobs, she worked for six years as a state-appointed duty lawyer, defending illegal immigrants facing deportation. “They are human beings who have rights,” she said recently in a TV interview. “We don’t blame immigration policies on them. It’s not their fault.”

At 30, she won her first role as regional councillor for the Front National in Henin-Beaumont, a depressed, former coal-mining town in the north, which she later made her political laboratory, a place to reinvent herself as a “defender of the people”. She recognised that France’s northern industrial belt, which had traditionally voted left, could turn to the Front National if the party stood not just against immigration, which remained its chief selling point, but for the victims of deindustrialisation and the financial crisis. “It used to be called her laboratory, but now it’s the place she still has an apartment, the region I think she feels most at ease in,” said Sébastien Chenu, who ran her northern campaign in the last regional elections. “She’s easy to approach. That’s why it works for her in the north. She likes the contact.”

Le Pen keeps her old friends close. “If anyone tried to betray her, they couldn’t stick around,” Chenu said. The Front National party-funding corruption cases currently under investigation – including allegations of misusing European public funds to pay French party workers, and false-accounting in election funding – have seen some of Le Pen’s closest childhood friends placed under formal investigation. They and the party deny all charges. But the cases showed how she had placed people she met at college in positions of trust.

Le Pen protects her children from the public exposure she had a child. Twice married and divorced from men who were active in the Front National, she had three children in the space of one year – a daughter immediately followed by twins. Her current partner is the party deputy, Louis Aliot.

She once described her feud with her father as “the hardest time of my life except childbirth” but hinted she expected him to call her if she won the presidency. Le Pen Sr’s idea of parenting was always about toughening up his daughter. When Marine Le Pen was 20, he took her to the morgue to see the corpse of a party figure killed in a car crash. When she asked why, he said: “I don’t want the first dead person you see to be me.”

Marine Le Pen during a campaign meeting earlier this week. Photograph: Chamussy/Sipa/Rex/Shutterstock

Marine Le Pen

Potted profile

Born: 5 August 1968

Career: She was legal officer for her father’s far-right Front National party before winning different councillor posts in Henin-Beaumont in the north and in Paris. Currently regional councillor for the northern region, Hauts-de-France. Member of the European parliament since 2004, where she co-heads the anti-EU grouping, Europe of Nations and Freedom – a bloc of rightwing nationalist parties.

High point: Taking over the leadership of the Front National from her father in 2011.

Low point: Failing to win control of any French regions in 2015 elections, despite topping the first round and massively increasing her party’s score. The left and right grouped together to oppose her.

What she says: “We’re thrilled that the British have seized this extraordinary opportunity to escape their servitude” – on Britain’s vote to leave the EU.

What they say: “A danger for France and a danger for Europe,” – European commissioner and former Socialist French economy minister, Pierre Moscovici.