The events of the past week in south-west France are destined to resonate far beyond the world of violent crime, and far beyond the region in which they unfolded, for two connected reasons. First, because of the racial, religious – and so political – dimension of the killings. But second, and crucially, because France is in the throes of a close-fought presidential election campaign, which was already likely to hinge on some of the issues raised by the shootings in and around Toulouse. The contest is likely to become much nastier, but also harder to read, as a result.

The release of the presumed gunman's identity and his personal history yesterday turned all the early assumptions about his killing spree on their head. He is not, as his choice of victims initially suggested, an adherent of the French far right, so the dark-horse National Front is unlikely to suffer by association – as its leader, Marine Le Pen, clearly feared. Instead, he was named as Mohamed Merah and described as a Frenchman of Algerian origin, who is believed to have undergone training in Pakistan by an affiliate of al-Qa'ida and been sprung from an Afghan prison by the Taliban. His cause was not that of "cleansing" France, but of opposing French military engagement in Muslim countries and supporting the Palestinians against Israel. His profile is thus more like that of the London 7/7 bombers, and this could change the whole dynamic of the election.

There is a bizarre irony here. When 69 young people were killed last summer on an island near Oslo, the initial presumption was that the gunman was motivated by Islamic fundamentalism. It turned out that he was a Norwegian, Anders Breivik, who was acting out his extreme right-wing views. In France, the presumption was the other way round.

The facts, as they are known, do not bode well for President Sarkozy. Not only might they push some centre-right voters further right, they could also call into question one of his key campaign pitches, his claim to be tough on law and order. After all, Merah seems to have escaped the attentions of French intelligence, with disastrous consequences. Nor, though, are the implications all positive for Mr Sarkozy's Socialist opponent, François Hollande. His more inclusive message is unlikely to go down well with French voters in coming weeks. Ms Le Pen and the National Front look set to gain the most.

That alone could tempt Mr Sarkozy to present himself as the strong man, flirt – more than he already has – with xenophobia, and try to push through the sort of illiberal legislation that the Labour government enacted after 7/7. While politically seductive, such a course would be ignoble. This is an instance where Mr Sarkozy needs to remember that his candidacy is less important than his current – and possibly future – responsibilities as President of all France.