As education minister, he tried to move more public money to private (ie, Catholic) schools, he's never been particularly well respected by public or private sector unions (unlike someone like Borloo) and his economic proposals would amount to deep cuts in public services.
Another question -- even though I think Royal may be down for the count (see my pessimistic analysis below), its also the case that presidential elections in France have been much more unstable than, for instance, the US. Just to give 2 quick examples -- in 95, Chirac came back from the dead in late February to take a big lead by mid-March, then barely held on to beat Balladur for 2nd in April; in 02, Jospin and Chirac both fell from mid-30s in Feb to 20s by election day. Here's one reason why -- when the formal campaign starts after March 20, all the qualified candidates (even the ones <1% in the polls) get equal time for ads as well as equal time on the news. And they can use it anyway they want -- the far left candidates may well use it to beat up Royal (as they did to Jospin in 02) and if LePen stays out and Sarko moves to the far right (as he seems to be itching to do), Bayrou may decide, for instance, to try to occupy the center-right. Or the consverse.
As one PS tactician said in LeMonde this week, "its an ice-skating rink right now and anyone call fall down" (my very free translation).
Please note that in the US there is no such thing. Even a major third-party candidate is nobody unless they are rich as far as the media is concerned.