Looks like he doesn’t want to spend money campaigning and then have a high probability of losing. The WI unions have spent money at a deficit on the recall elections and the Judge Prosser election, and that leaves them very lean going into 2012.
The union money has one arrow left in the quiver - try to turn at least one member of the Wisconsin state senate from a nominal “R” to a practicing “D”.
But this leaves little latitude for a person now out of office to be able to worm the way back in.