You can argue that the right wing of the PS is really center-right. However, you then also have to accept that the French electorate tilts sharply right and simply doesn't want left wing policies.
Libe aims for the right wing of the PS, nowadays (for example they were for the Yes in the Constitution referendum). This has changed in the last few years. They are anti-Sarkozy, but increasingly (Euro-)liberal in their economics commentary. They are center left at best, in their current incarnation.
As for the French electorate - the 2007 presidential election represents the French opinion badly, as on the left it was skewed by the need to have somebody from the left in the second round. In 2002, and in various regional elections, people calling themselves Communist gathered 15% of the vote, with other parts of the left, like the Greens, getting another 10%... And the right wing of the PS has pretty much joined Sarko. The PS has bee to the right of its electorate for quite some time. Un roi sans divertissement est un homme plein de misères
