The week had started so well for French socialists. Parisians and le peuple de gauche were treated with a concert at the Bastille to celebrate the 30th anniversary of François Mitterrand's election on 10 May 1981. The socialist philanthropist Pierre Bergé, Yves Saint Laurent's former partner, had paid for the celebrations. At news-stands, special editions showed the dignified profile of the man we called the Sphinx, the only Socialist president of the Fifth Republic.

To many observers like me, such celebrations felt too nostalgic. The battle was ahead of us, not behind: why celebrate the past when there was so much work to do? With the presidential elections looming, we would see an epic battle to regain power, at long last, after 17 years in opposition. The whole Mitterrand mania seemed slightly indulgent and passéiste.

However, we could take heart at the prospect of Dominique Strauss-Kahn, head of the International Monetary Fund (IMF), being inducted as the presidential candidate for the left. Poll after poll had placed him ahead of everyone else. In a few weeks' time, he would resign from the IMF and announce his candidacy. It was hoped that, 12 months later, he would be able to put a close to Nicolas Sarkozy's five disastrous years in power. Many were relying on him to restore France's standing.

Paraded and shamed

The 64th Cannes Film Festival opened on Wednesday 11 May. We watched the Italian director Nanni Moretti's Habemus Papam, a dark comedy about a newly chosen pope who is unable to carry out his public duties because of his fear at the idea of addressing a billion Catholics. This was a portrait of a man in crisis. Then came the unimaginable, the unthinkable. Reality was wilder than our worst nightmares. The news reached us that Strauss-Kahn - whom we expected would be France's next president - had been arrested on board a Paris-bound Air France flight, ten minutes before take-off. Charged with what? The attempted rape of a hotel worker. The nation was in a state of stupor.

It could only be a set-up or a honeytrap. Or, perhaps, an Anglo-Saxon conspiracy. Was the CIA involved? A plot by Sarkozy? We didn't want to believe it. Our brains would not process the information that the New York police were giving us. Non, non, non.

But worse was still to come. First, there were the images of DSK emerging from a Harlem police station, his hands cuffed behind his back. Handcuffed! A shiver went down the spine of a nation. In France, such images are illegal. A law passed in 2000 to preserve the presumption of innocence prevents images of handcuffed suspects being published or broadcast until they are proven guilty.

The US legal system had appeared before us in all its ancien régime cruelty: the accused paraded and shamed in public before he could even speak. The New York police told French journalists that they wouldn't be able to film the victim but would have plenty of time to film Strauss-Kahn being hustled away to court.

In France, it is illegal to film a courtroom hearing. But not in the US. The images of DSK facing Judge Melissa Jackson were another nail driven into the French psyche. And then the coup de grâce: the announcement came that Strauss-Kahn would not be released on bail. Many American lawyers expressed their surprise; apart from murderers, New York judges grant bail to most suspects. How could DSK risk fleeing with his ankle tagged and after paying $1m in bail?

The prosecution mentioned the name of Roman Polanski. Polanski? What on earth had he to do with DSK? While he spent his first night at the notorious Rikers Island prison, the backlash started. The New York Times unleashed an attack on the culture of secrecy in France, whereby politicians' alleged sexual vices are kept away from the wider public. French journalists knew all about DSK's womanising. Why didn't they denounce him?

“Denounce what? Extramarital affairs? What for?" I replied to an American colleague. The distinction in France between what is private and public is quite clear. To be a libertine is not to be a criminal. Look up the word in the dictionary. A libertine was first of all a freethinker. Sex between consenting adults, within or outside marriage, is simply nobody's business. Even when it comes to politicians. Being accused of a rape is, however, a different matter. The offence makes it a public affair. But could we have prevented the alleged attack, as many among the American media hinted, by revealing DSK's extra-large libido?

What should we have written about DSK? No woman had ever filed complaints about his attitude. Yes, he was known as an insistent flirt. There is no law in France making that a criminal offence. Perhaps this should change; it is an issue France is now starting to address.
In the meantime, the Socialist Party is in disarray. The political landscape is now a white canvas. Sarkozy, soon to be a father for the fourth time, is looking, by contrast - and for the first time in years - almost presidential. His horizon has been cleared, miraculously. The Front National leader, Marine Le Pen, who claims to be fighting a crusade against a corrupt French elite, is rising in popularity in the polls.

The question now for the Socialist Party is who should replace Strauss-Kahn as presidential candidate. Martine Aubry, daughter of Jacques Delors and architect of France's 35-hour working week, may be too antagonistic a choice if the party wants to reach out to the centre-right. Or should it be François Hollande, former partner of Ségolène Royal, who ran for the presidency in 2007? He is bright, able and genial and looks like the best choice. One thing is clear, though: the party's séducteurs should adopt a low profile.

Agnès Poirier is a French journalist based in London