But outside France this epic duel, being fought out in a time of economic crisis, has already been framed according to certain assumptions - assumptions not necessarily correct.
But so prevalent have they become that they risk skewing the international response, when the victor's face emerges, in time-honoured manner, on French TV screens after the polls close on Monday.
The first assumption is that Sarkozy, the incumbent President, is certain to lose. It is true that all opinion polls on the eve of the debate had him trailing the Socialist, Hollande, by about six points (47 to 53 per cent); that the gap has been quite consistent since the first round the Monday before last; and that six points is a lot to make up with very little time to do it.
But some caveats are in order. National Front leader Marine Le Pen's almost 18 per cent of the first-round vote has to go somewhere.
The French are conscientious voters (as witnessed by the 80 per cent turn-out on April 23), and by no means all will follow Le Pen in leaving their ballot papers blank. Not all those votes will go to Sarkozy, for all his increasingly shameless efforts to win them, but some will.
Add to this the slight narrowing of the polls over the past week, and the fact that the full impact of the debate will be felt only in the actual vote.
Sarkozy failed to land the killer blow; he came across as aggressive, ill-tempered and self-absorbed. But such attributes will not necessarily be condemned by voters craving a President who will stand up for France.
His challenger came across as almost equally ill-tempered, with less rapid-fire repartee, and less experience. Sarkozy is a fighter, and it is not over yet.
The second assumption - sometimes aired by Sarkozy supporters to frighten waverers, but more often brandished abroad - is that if Hollande is France's next President, he will have to tack to the left to placate those who cast their first-round votes for the far-left candidate, Jean-Luc Melenchon.
But this neglects two realities. The first is that, although Melenchon performed creditably, he did not make the breakthrough his campaigning charisma had suggested. The second is that the political complexion of France, as revealed by the first-round vote, still tends more to the right than to the left. That is the France that awaits the next President, whoever it turns out to be.
The third assumption outside France is that a Hollande victory would spell meltdown for the euro.
Such thinking is based partly on the fact that Hollande is the Socialist (and so, it is supposed, the less fiscally responsible). And, of course, Sarkozy traded on this in the debate.
It proceeds also from Hollande's emphasis on "growth" over "austerity", and from his election pledge to reopen the European Fiscal Stability Treaty.
But the logic of these arguments is questionable. "Reopening" does not have to be the same as "renegotiating", and there are many other imponderables - the Irish referendum, the Greek election, the Spanish economy - which suggest the treaty may not be set in stone.
The main reason why a Hollande victory will not trigger an immediate euro crisis, though, is that the financial markets have already anticipated such a result. The wobble, in so far as it happened, followed Hollande's first-round victory and subsequent polls forecasting an easy second-round win.
As for commitment to the European project, French Socialist leaders have been at least as communautaire as their Gaullist counterparts, and sometimes more willing to cede small pieces of national sovereignty to the common cause. Hollande will not break that particular mould.
The fourth assumption outside France is that Hollande's arrival at the Elysee would damage the Franco-German engine that effectively holds Europe together. The claim here is that Angela Merkel not only shares a centre-right world view with Sarkozy, but has invested so much in a difficult personal relationship that a new start with a Socialist leader would be worse. But would Merkel really find Hollande a trickier proposition than Sarkozy? German and French leaders of different parties have often hit it off better than those of supposedly like political mind, while character-wise, Merkel - cautious, solid and consensus-seeking - would seem to have more in common with Hollande than she ever had with Sarkozy. The big ideological divergence - growth versus austerity - might even become more bridgeable in their hands.
Which leads on to the fifth, and last, false assumption: that a second term for Sarkozy would mean more of the same, while his defeat would effect a break with the past of the sort he promised five years ago, but mostly failed to deliver.
In fact, Sarkozy's failure illustrates the limited room for manoeuvre that any national leader has in straitened times, whatever their promises and ideology. At the same time, however, Europe's tolerance for unadulterated stringency seems to be shrinking, with a serious search on for ways of generating jobs, if not rapid growth, without busting the budget.
And Germany, with its low unemployment and comparative social peace, is the euro country that sets the standard here, too, as it does for living within one's means.
Sarkozy's stump speeches and debate answers show that he, no less in fact than Hollande, has been contemplating adjustments in the austerity/growth ratio. The upshot is that, whoever wins on Monday, left or right, is probably destined to be - in the words of Hollande's campaign slogan - the President of change.
- Independent
