The French presidential election campaign has thrown up its customary cast of colourful characters and, in recent weeks, a fast-moving succession of polls that show President Nicolas Sarkozy and his Socialist challenger, François Hollande, running neck and neck to the finish. But tomorrow's election is the only poll that matters, and the map of French opinion it reveals will be as keenly awaited as ever. With one in four voters still said to be undecided as the bar came down on campaigning, the political future of France, and to an extent that of all Europe, is entering a two-week period of suspension.

The first round of any French presidential election can be described as a rehearsal for the real contest, between the two front-runners, and a playground for protest voters. That does not mean, however, that it has no significance. The left-wing candidate, Jean-Luc Mélenchon, has become a realistic contender for third place not just because he is, like many minority candidates, an attractive personality and an energetic campaigner, but because he has tapped into a strain of sentiment in France that is troubled by increasing social inequality. If his election performance matches his showing in the opinion polls, this could launch the far left into a position of national influence after the legislative elections in June.

Marine Le Pen, like her father before her, has played unconscionably on public misgivings about immigration and society's supposed loss of "Frenchness", despite at the same time trying to update and sanitise the party's image. Like her father, too, she threatens to be the dark horse coming up on the outside. That French voters drawn to the far right tend to dissemble their voting intentions has led to their actual performance being routinely underestimated, despite efforts to weight the opinion polls to compensate. The latest polls showed Ms Le Pen commanding as much as 17 per cent of the vote – which would equal the best National Front showing of recent years.

Thankfully, that would almost certainly not be enough to propel her to second place and into the run-off – emulating her father's cataclysmic "April surprise" of a decade ago. The inoculating effect of that 2002 vote and the more credible campaign of the Socialist candidate, Mr Hollande, compared with that of Lionel Jospin, both militate against Ms Le Pen reaching the second round. But a strong National Front performance still holds considerable dangers, showing – as it would – the continuing appeal of a xenophobic platform in France and perhaps presaging the return of the far right to the National Assembly.

Ms Le Pen's resort to anti-foreigner rhetoric in the wake of the Toulouse shootings last month must also carry much of the blame for the sharply rightward shift in Mr Sarkozy's electoral discourse as the campaign reached its latter stages. Once again, the National Front has helped to set the tone and the terms for an election that, to the credit of the French electorate as a whole, it has not the slightest prospect of winning.

The other chief criticism of the first-round campaign is that it has focused on personal character (diverse in the extreme) and national mood (gloomy), to the exclusion of the serious policy debate that France needs to have. But that is where the fascination, and the significance, of the next two weeks could lie. Assuming a classic duel between centre-right and centre-left, Mr Sarkozy against Mr Hollande, France – and Europe – must hope for a demonstration of democratic politics at its best and a debate that will really matter.