Even if he doesn't resign, might Bauer's endorsement hold more weight than Sanford's at this point?
At this point endorsements don't matter at all; neither does Sanford. Depends entirely on whether Bauer manages to win the Governor's race against McMaster and Barrett. If Bauer loses, which I devoutly hope, he's toast and his endorsement is unlikely to sway anybody in 2012. While he and Sanford have not gotten along well, both have used the same fresh young blood theme to their advantage, a theme I expect will not play well in 2010.
Bauer might be able to garner enough votes to make the runoff, but I don't think he'll win it, though he does possess the advantage that voters can be confident he won't cheat on his wife, since he doesn't have one while both McMaster and Barrett do.