EVER since Marine Le Pen became leader of the National Front (FN) in 2011, her father, Jean-Marie, has lurked in the background like a piece of unexploded ordnance. He may have stepped back from leading the party that he founded in 1972, but the 86-year-old is honorary president and an FN member of the European Parliament. His next ambition was to stand for election in December to the southern region of Provence-Alpes-Côte d’Azur.

Yet Mr Le Pen’s taste for explosive provocation got the better of him. Earlier this month he repeated a comment made in 1987 that the Nazi gas chambers were a mere “detail” of history. Ms Le Pen, who has tried to detoxify the party’s brand and bury its anti-Semitism and racism, threw a fit. She accused her father of “political suicide” and of imperilling the party’s future. The FN leadership, she said, would no longer back his candidacy. A dynastic psychodrama began, with Mr Le Pen accusing his daughter of “sabotage”. At one point, it looked as if he might be thrown out of his own party and even run against it.

In the end, Mr Le Pen withdrew his candidacy to avoid “dangerously weakening our movement”. He proposed that the party should nominate his granddaughter, Marion Maréchal-Le Pen, one of two FN members of parliament, in his place. Mr Le Pen, his granddaughter said after speaking to him, did not want to make things worse and was even “a bit sorry about the situation”. The immediate upshot was a victory for Ms Le Pen in her bid to transform a far-right, fringe protest movement into a mainstream party ready to govern. Mr Le Pen was all about grumbling and outrage: he never really wanted power. “Jean-Marie Le Pen worried very little about demonstrating that his party was fit to govern,” says Sylvain Crépon, a specialist on the FN at the University of Tours.

His daughter, by contrast, wants to remake the French party-political landscape, establishing the FN as a credible alternative to the ruling Socialists under President François Hollande, and to the centre-right UMP party, ahead of the presidential election in 2017. The party’s recent gains in local and European elections are seen as crucial to building the army she needs for a presidential bid. In the public mind, sidelining Mr Le Pen in such spectacular fashion will have reinforced her transformation.

The interesting dynamic now will be between Ms Le Pen and her niece, Ms Maréchal-Le Pen. The youngest member of the political clan was elected to parliament in 2012 when a 22-year-old law student, and has been close to her grandfather and the FN’s traditional right. They are sceptical of Ms Le Pen’s bid to woo working-class voters with a protectionist, anti-globalisation, big-government line. Mr Le Pen has called the party’s proposal to reduce the retirement age to 60 an “absurdity”.

Yet Ms Maréchal-Le Pen seems a canny operator, who knows she embodies a younger generation little taken by her grandfather’s crowd. She is careful to stress her loyalty to her aunt. “I am clearly in the National Front of Marine Le Pen,” she said this week. Each needs the other. The niece has her base in the south, a traditional FN bastion; the aunt has put down roots in the ex-industrial north. Both seem to have gained from the family feud. Each rose a place in the latest popularity rankings by Ifop, a pollster—with Ms Le Pen just above Mr Hollande, and Ms Maréchal-Le Pen only three places lower.