There is an air of inevitability about today's second and final round of France's presidential election. All opinion polls indicate that Mr Emmanuel Macron, a centrist politician who supports free trade and wants to maintain open borders to migrants, is almost guaranteed to win against Ms Marine Le Pen, the leader of the far-right, anti-immigrant National Front.

But behind this mood of certainty, France remains restless. For almost everything about today's ballots and what will follow immediately thereafter is unpredictable.

Much will depend on how many men and women choose to go out and vote today. For, coming just two weeks after the first round of the presidential election and pitting themselves against each other, the two candidates who led all opinion polls for many previous months can cause voter apathy.

All analysts agree that a low turnout will mostly hurt Mr Macron, partly because abstentions are likely to come from those who believe that his election is already guaranteed, but also because Ms Le Pen's National Front supporters are traditionally much more disciplined and motivated.

The margin by which Mr Macron wins today is politically important. If he gets more than 60 per cent of the votes cast, this will be interpreted as a strong rebuff not only to the National Front, but also to Europe's far-right populists and anti-immigration politicians.

But if Ms Le Pen manages to get more than the 40 per cent of the ballots, she will claim that she still faces a bright political future. The National Front leader is already preparing the ground for her post-electoral fight by warning of an "anger that will explode in this country" should Mr Macron, whom she dismisses as "indifferent to France's national interests", become president.

Last Friday's anonymous leak of a large stash of Mr Macron's campaign e-mails, apparently stolen from the hacked computers of his aides, is unlikely to affect voting, if only because the leak came after a legal ban against any electoral debates entered into force in France, thereby precluding both candidates from commenting on the supposed revelations.

But the leak, which Mr Macron's officials are already blaming on Russia's intelligence services, confirms the impression that this was one of the ugliest and most ill-tempered campaigns in modern French history. And soon after ballots close, France's media is guaranteed to start digging into the dump of stolen e-mails for any bit of titillating information against the man who is likely to be their newly elected president.

To complicate matters further, Mr Macron is an untested politician. Apart from a brief spell in France's outgoing Socialist government, he never stood for any elected post and has no political party organisation behind him. But, if he is to govern effectively, he will need to be a player in the parliamentary elections, which follow next month.

Mr Macron insists that his own hastily established "movement" will turn into a party that will obtain a "clear majority" in Parliament; he dismissed as "absurd" suggestions that he would have to live with a hostile legislature.

But with only weeks at his disposal to create a parliamentary organisation from scratch, the idea that a newly formed Macron party would end up gaining the 290 seats required to have a parliamentary majority remains far-fetched; a much more likely outcome is that Mr Macron will have to live with a legislature in which the centre-left Socialists and centre-right Republicans continue to call the shots.

And that will mean more rather than less friction, as both of France's mainstream parties regard Mr Macron as their chief threat, and neither has the slightest interest in seeing his presidency succeed.

So, while Mr Macron's advisers are already chilling the champagne bottles for tonight's victory celebrations, their candidate knows that he will not enjoy much of an electoral honeymoon.