"Borloo, c'est un zozo," François Fillon is supposed to have said back when Borloo was rumored to be in line for Fillon's job. Now Borloo has his revenge. His move yesterday to quit the UMP and explore the opening for a new party in the center is a finger in the eye of Sarkozy--and in the eyes of the squabbling heirs apparent of the tattered Sarkozy mantle, Fillon and Copé. A Borloo candidacy would increase the probability of a Sarkozy defeat in the first round and possibly increase the likelihood of a victory for Marine Le Pen--and therefore of the Left in the second round. So what is Borloo's game? Does he think he can create enough of a dynamic in the center actually to prevail in the first round? It's possible but not entirely in his control: this would depend on the nominee of the Left. If DSK is chosen, I can't see this happening.
So assume that DSK does run? What does Borloo want? It would be plausible to assume that he'd want some kind of promise from Sarkozy in return for ending his candidacy after a decent interval and returning to the fold. Prime minister? Would he really want to serve under Sarko after his public humiliation last year? Perhaps. Politicians are prepared to swallow a great deal in return for power. A stint as prime minister would make Borloo more présidentiable in 2017. But maybe his candidacy is more visceral than that. Maybe he just wants to screw Sarko after having been seduced and abandoned.
It has now become impossible to describe the French presidential field to anyone who hasn't been following French politics for a while. There are just too many variables. This can't last. After DSK gets in or out, I would look forward to some sort of simplification.