My sense has been for two years this:

1. the French want a "different" kind of President who provides a rupture;

2. Sarko was the only candidate offering this, for two years;

3. But Sarko is not liked or trusted by the electorate;

4. If a viable alternatitve offering change appears, he s/he will win;

5. Sego looked like she might be that candidate last year, but she has proved to be a fairly standard issue socialist

6. Bayrou has now broken through an important threshold and to me seems the perfect candidate for what the French electorate wants - at least, say, the middle third; I feel his momentum will build on itself and attract voters from across the spectrum

7. This could also have the effect of splitting Sego's left flank;

8. I also think a lot of the undecided/fuck you LePen vote will go to Bayrou

9. Bayrou's main challenge in the 2nd tour will be to hold his ground; Sarko's only real attack willl come about his ability to form a national unity gov't; I've already seen this tact previewed by nervous Sarko supporters elsewhere