Why the two-timed French First Girlfriend Valerie Trierweiler faces some harsh choices

What a difference a week makes. Only on Monday, Valerie Trierweiler, France's informal First Lady, recently back from Africa where she had been handing out French aid subsidies to selected charities, was hosting an exclusive private screening of Yves Saint Laurent, the acclaimed biopic on the late couturier produced by his influential partner, Pierre Berge.

At the cocktail party that followed, where la Gauche caviar - fashionistas, Vogue Paris editors and cabinet ministers - mingled under the gilt ceilings of the Elysee over champagne with a few handpicked political journalists, the president's elegant partner distilled confidences amid the air kisses. Ranging from how hard "Francois" was working "for France" to her plans to extend her own charitable missions to India, she consciously positioned herself somewhere between her political model, the late Danielle Mitterrand, the socially conscious wife of France's only other Socialist Fifth Republic president, and a kind of Republican Princess Diana.

At that very moment,Trierweiler could have been forgiven for thinking that, at last, after a very rocky start, she had established her problematic role as the country's First Girlfriend - the unmarried partner of a 59-year-old president who had never quite wanted to tie the knot with anyone. That was then.

On Saturday, after Friday's claims, backed by apparent photo evidence in the gossip magazine Closer, that President Francois Hollande had been two-timing her with an actress almost a decade her junior, Trierweiler is pondering her options from the safe haven of a friend's flat elsewhere in Paris. Notoriously insecure, she is not comforted by the fact that the decision may not be solely hers to make: Hollande's political advisers, currently bunkered down at the Elysee in crisis mode, have advised the president, who is scheduled to give a major press conference next Tuesday, that he must make "a clean sweep" within the next 48 hours.

Otherwise, they warn, his formal political announcements risk being overshadowed by speculation about his private affairs. The president apparently knows of more alleged pictures being offered to Paris magazines. He has not denied he was seeing Julie Gayet, 41- the daughter of a personal friend, the renowned Paris surgeon Professor Brice Gayet.

"A clean sweep" therefore can only mean enacting Trierweiler's departure. Rumours that an official communique from the presidency would come this weekend made the rounds yesterday, though all were shot down for now at least by Elysee sources. Clean sweeps are what Mr Hollande has spent a lifetime avoiding, in his private as well as in his political life. The highly regarded political journalist Cecile Amar, in her forthcoming presidential biography tellingly entitled Jusqu'ici, tout va mal (So far, everything is going belly-up), tells of Elysee aides being harshly reprimanded but never let go; of political enemies alternately frozen out, then brought back into the cabinet because Hollande believes he can control them better there.

Everyone in France knows that Hollande maintained for several years the polite fiction that he still lived with Segolene Royal, the mother of his four children and his partner for 23 years, even though he had moved to Trierweiler's 15th arrondissement flat. All that while, political journalists happily traded among themselves the names of many beauties who were apparently being squired by the then Socialist Party's first secretary. As a friend of the conservative former president Jacques Chirac and as a former youthful aide in Francois Mitterrand's Elysee, Hollande presumably felt he could bank on the traditional French attitude to politicians' privacy.

His official reaction to the Closer allegations has been to "greatly deplore [the] invasion of his private life, to which he has a right as any other citizen does", no doubt recalling his mentors' long-unreported escapades. Mitterrand ran three parallel families, with two illegitimate children from two different women in addition to the two sons he had by his wife, Danielle; Chirac, a notorious womaniser, had among dozens of affairs a long liaison with the actress Claudia Cardinale, whom he openly escorted to parties in Paris. Yet all indications are of a sea change in French attitudes. All over the internet, unscientific but massively answered polls show the same implacable proportion of hostile reactions.

Of 45,000 respondents to "Does his affair with Julie Gayet make the President look more sympathique or discredited?" on the Closer website, 78 per cent answered "discredited". Out of nearly 3,000 answers to the question "Should politicians' private lives be off-limits?" on the site of Challenges, France's closest answer to The Economist, 77 per cent said "no".

This comes as a sharp contrast to the touching unanimity displayed by almost all leading French politicians, from the far Left to the far Right, who all protested that Mr Hollande's private life should be his concern only. It was, perhaps, predictable: just as British voters turned against tin-eared MPs at the time of the expenses scandal, the French public is outraged that politicians seem to guard one another's backs. The outrage was first apparent when the IMF president and Socialist presidential hopeful, Dominique Strauss-Kahn, was arrested in New York three years ago. It is compounded today by Mr Hollande's record unpopularity: nobody wants to cut him any slack. The president is not helped by the apparent tawdriness, of the whole affair.

Pictures of a crash-helmeted Mr Hollande riding on the back of a scooter driven by his security officer the 300 yards from the Elysee garden gate to rue du Cirque, where he was meeting Miss Gayet, make him look faintly ridiculous. The flat is said to belong to a friendly billionaire and to have been used over the years for other discreet assignations among the political class: if true, how would such favours differ from the oft-reproached yachting holiday to which Nicolas Sarkozy was invited after his 2007 victory? The Closer pictures also show the president's security officer bringing a bagful of croissants in the morning to the couple's hideaway: the republican French don't take very well to the Jeevesisation of their policemen.

And yet it is possible that Mr Hollande may shy away from taking a final decision over what to do about his women between now and Tuesday. In which case Ms Trierweiler may face the harshest choice of them all: whether to go back to the Elysee under the nation's mocking glare, despite her partner's betrayal, or to throw to the wind everything she has built in the past decade. She may yet regret having treated Segolene Royal so badly.