On Sunday French voters go to the polls in the most important and unpredictable presidential election for 26 years. Even at this stage, more than two in five are still undecided, and the main candidates in a crowded field of 12 are desperately searching for support, often in questionable areas, to win through to the all-important run-off. Although the campaign has only just begun formally, it has in fact been in full swing all this year. And by this stage it is becoming dirty, with accusations and innuendos intended to fan prejudices and damage rivals but that have left the real issues — the economy, the need for reform and France’s place in the world — almost untouched. The polls remain as confused as the voters, and there are likely to be wild predictions and improbable scenarios in the coming week.

Nicolas Sarkozy, the combative former Interior Minister and head of the main conservative party, remains the front-runner. But his lead is far from unassailable, and in recent weeks a powerful “Anyone But Sarkozy” movement has emerged, grouping supercilious civil servants, leftwing professionals, the 1960s generation and all those who fear that his straight talk on the economy and the need for “rupture” with the social consensus threatens their interests. He is being portrayed as a demagogue who would exacerbate race relations, dismantle much of France’s cherished social security structure and Americanise French society in all the ways that produce scornful disdain among traditional Gaullists.

But although he has lurched to the right in fields such as immigration, in a transparent and not wholly creditable attempt to woo those tempted still by the xenophobic nationalism of Jean-Marie Le Pen, he remains, by far, the more convincing candidate. This is partly also because of the weakness of his rivals. Ségolãne Royal, the Socialist Party candidate, has the glamour, freshness and courage of being the first serious woman candidate, but has proved an erratic lightweight, an incoherent debater and an old-fashioned leftwinger with little understanding of how clichéd and dogmatic socialism has failed the country in the past. If she can make it to the second round, her faltering campaign may take on a new dynamism and legitimacy. But like her hapless socialist predecessor last time round, she may stumble, leaving voters with no leftwing alternative.

The third candidate, François Bayrou, has not achieved the momentum needed to establish credibility, despite coming close in recent week to the front-runners. He is a bland figure, who may benefit from visceral suspicion of the other two but who is stuck with old ideas on state intervention and is vague about how he would form a government from such a narrow political base.

Depressingly, however, all candidates have been wary of voicing the real challenges: France’s low growth, entrenched opposition to change, unrealistic labour and workplace regulations and moral funk in the face of globalisation, European Union reform and economic liberalisation. An old-fashioned and nostalgic Gaullism still casts a powerful spell.

The exception remains Mr Sarkozy. Although he, too, is fearful of spelling out the costs and implications of change to the French model, his reforming instincts remain strong. He understands the need to repair relations with America, tackle the extremism and alienation of immigrant ghettos, cut taxes and get a sluggish economy moving. He deserves to stride into the second round with a commanding lead.