His main problem is that for ideological reasons (split between conservatism and an out of tune left) and the election system in itself, it's very difficult to break through...
but not impossible
As for your reference to Royal reverting to an imagined "Jospinism" you apparently disdain (despite the fact that the only period of growth, unemployment reduction and income gains in the past two decades was under his government...) I'm wondering how you would make this comment in light of your comment that Bayrou is some antruistic rallier of all French, citing as you do the fact he would name DSK as PM.
DSK is, for all intents and purposes, at the core of Jospinism. Fai de bèn a Bertrand, te lou rendra en cagant