The first round has many candidates (if they can get those 500 endorsements - assuming this blog has the numbers right, I think Le Pen will manage it, since 500 out of 45,000 is not that difficult, for someone on 19% popular support - normally 4 or 5 left wing candidates manage it, and I think Marin Le Pen's father always managed it, and she's said to be a bit more 'personable' than him:
A candidate in the first round must obviously be a French national and must have obtained the signature of 500 elected people from at least 30 different departments in France or abroad. There are potentially 45 000 elected people, including 36 000 Mayors. No one can present more than one person in the election.
http://johninparis.blogspot.com/2011/12/french-presidentials-race-for-500.html
36,000 mayors is a lot - France has a mayor for each village, and the Nationalist message plays better in rural areas. After that round, the top 2 face off in the final round:
French President Nicolas Sarkozy narrowed challenger Francois Hollandes lead in opinion polls, according to an Ifop survey in Le Journal du Dimanche today.
The Socialist Hollande leads the incumbent in a head-to- head contest by 54 percent to 46 percent, a 4 point swing in Sarkozys favor from last month, the poll showed. Sarkozy gained 2 points and Hollande lost 2 points.
In the multi-candidate knockout voting round, Hollande would take 28 percent, up by 1/2 a point, and Sarkozy would win 26 percent, up 2 points. National Front candidate Marine Le Pen would get 19 percent, down one point.
http://www.bloomberg.com/news/2012-01-08/sarkozy-narrows-socialist-hollande-s-poll-lead-ifop-survey-says.html
So it's still possible that Le Pen could end up in the runoff against Hollande, if things go bad for Sarkozy (eg the economy). A face-to-face between Hollande and Le Pen should be comfortably won by Hollande, though - a poll said up to 30% would consider voting for her, which indicates there's still a large part of the centre-right that finds her too extreme.