A new book entitled Entre Deux Feus - which translates as Between Two Fires - offers insight into how the feud between Francois Hollande's partner and former partner has strayed into matters of political importance.
Ménage à trois still burning the French president
Marseille, France // As if unemployment, the euro crisis and other pressing issues were not enough to keep Francois Hollande busy as the new French president, the two women closest to him have become a source of unwelcome distraction - with no sign of fading away.
It is an open secret in French political and media circles that Mr Hollande's first lady, Valerie Trierweiler, and the mother of his four children, Segolene Royal, detest each other.
Despite the president's aversion to details of his domestic life becoming public, the feud has brought not only massive media attention but, now, a book devoted to it.
France has traditionally viewed itself as above what is sees as an "Anglo-Saxon" obsession with intrusion into the private lives of prominent people.
However, this principle has been eroded in recent years and, in the case of Mr Hollande, there is also an inconvenient exception - the stormy relationship of the women in his life strays into matters of political significance.
The investigative journalists Anna Cabana and Anne Rosencher are the co-authors of the book, Entre Deux Feus - which translates as Between Two Fires.
They say that one difference between Ms Trierweiler and her predecessors at the Elysee is her willingness to speak out in defiance of her partner.
By contrast, Cabana told the French newspaper Le Journal du Dimanche, the equally strong-willed former wife of the last president, Nicolas Sarkozy, never publicly contradicted him.
To the dismay of Mr Hollande's supporters, and reportedly his own fury, Ms Trierweiler tweeted a message of support to a socialist rebel, Olivier Falorni, before he defeated Ms Royal in June's parliamentary elections.
She later said she regretted the controversy caused by her intervention and promised to pause for reflection before future use of Twitter.
But the authors say that while the offending tweet was not premeditated, her support for Ms Royal's opponent certainly was.
Cabana reports a conversation over coffee in Cafe Flore, a fashionable restaurant in Paris's Latin Quarter, in which Ms Trierweiler told a friend: "We are submissive until May 6 (the day after the deciding second round of the presidential election won by Mr Hollande). But after that, we'll back Olivier."
The authors also say they were told by Ms Royal - a highly experienced figure of the French left, who stood unsuccessfully against Mr Sarkozy in the 2007 presidential elections - that she was kept out of Mr Hollande's first cabinet on the express instructions of Ms Trierweiler.
Old-fashioned jealousy has been reported in the French media as lying at the heart of the women's mutual antipathy.
Ms Trierweiler, a journalist, replaced Ms Royal in the affections of the president but resents the hostility she feels was shown in response.
"To prove the issue is eminently political," said Cabana, "certain Hollande advisers have suggested to him that he should marry Valerie Trierweiler so that she has what Royal never had."
The authors also dwell on what they see as the "untenable" contradictions of Ms Trierweiler's position.
"What is striking about the SMS [controversy], as in other ways, is the extent to which she asserts her impulsiveness, this need to exist at any price. There is a real pain … she wants the gold of the Republic and wants to go on being a journalist. She had a choice, though. The French would be mature enough to understand her telling them, 'I want neither the title nor position of first lady, I will never appear publicly'. Or she could say 'I'll give up the job'. But she doesn't want to give up anything."
Ms Trierweiler's style and influence have also been examined by another author. The award-winning novelist, Laurent Binet, enjoyed remarkable behind-the-scenes access for his book of the Hollande election campaign, Rien Ne Se Passe Comme Prevu - Nothing Goes As Planned.
Asked by the magazine Nouvel Observateur whether Ms Trierweiler's views were taken into account in political meetings, Binet replied: "He listened to her, just as he listened to his son Thomas. Therefore yes, I think her word carried some weight."
It is reported that Thomas Hollande, who also advised his mother during her presidential challenge, and his siblings want nothing to do with Ms Trierweiler.
The animosity between their father's partner and their mother is not all one way. Ms Royal is alleged by Ms Trierweiler to have attempted to have her removed from her post as a political writer because of her relationship with Mr Hollande.
But nothing, in the judgement of the authors of Between Two Fires, competes for significance with the infamous tweet.
"She sent it from the first lady's quarters in the east wing of the Elysee while the president was in his office, a geographical illustration of the supreme transgression that turned a private psychodrama into a state scandal," said Cabana. "With that tweet, she opened the door to the president's bedroom."