Two hours into the rudest presidential TV debate in French history, something unusual happened. François Hollande became the president; Nicolas Sarkozy became the challenger. Mr Hollande launched into a speech in which he explained how he would be a different, more consensual president than Mr Sarkozy. He began each sentence with "Moi, President, je..." ("I, as President will...").

The Socialist front-runner had dressed daringly, given his reputation for dullness, in a grey suit and matching grey tie. Suddenly, he seemed transformed from the balding "Monsieur Normal" to the President of the fifth-largest economic power in the world.

Mr Sarkozy, all nervous tics and shoulder movements, stared glumly at his notes. He stopped, briefly, calling Mr Hollande "a liar". It was the moment, perhaps, when President Sarkozy realised that he had lost the debate. Whether he has lost the election remains to be seen.

He boasted beforehand that he would "tear Hollande to shreds". From the first minutes of a nearly three-hour debate, Mr Sarkozy launched into the attack. He complained that Mr Hollande's friends had been implying he was a fascist. And your friends, Mr Hollande retorted, have been calling me "every name in the zoo, the whole bestiary... You will have trouble passing yourself off as a victim, as a lamb."

It was the first of several Hollande "zingers" as they are called in US presidential debates.

Mr Sarkozy tried to argue that, despite falling living standards, his record during the crisis was better than that of most other European leaders. Those things which had gone wrong were the fault of previous governments. "You are always happy with yourself; it's just extraordinary," Mr Hollande said."

The President scored some points. He led Mr Hollande into difficulties on his vague proposals for controlling illegal immigration and his promise to hire 60,000 new school staff. But Mr Sarkozy's aggressive tactics boomeranged. He had expected the Socialist to wilt under pressure. Instead, he proved that he is a tougher man than he appears. And a President-in-waiting?