As noted on
kos, the correct move for the President would have been to invite Cleland to the ranch privately. A rejection by Cleland would appear ungrateful or partisan, while an acceptance of the offer would make Bush appear fair and confident.
Thankfully, it didn't occur to them to do that.
On the whole resignation issue, it now appears that there were sufficient contacts between Bush2004 and the SBVs to violate laws prohibiting coordination of campaign activities. There's no telling where this will go, though it looks like an issue that might stick around.