How are these scenarios are threat? Seems to me these would be win/win for establishment Republicans. A "bipartisan" ticket combining a McCain (or a Bush, or Romney) with a Clintonite liberal isn't so much bipartisan as an acknowledgement that we really have a single party that's been masquerading as two since 1989.
A McCain/Kerry ticket in the middle of the Iraq war, both of them veterans, running against the AWOL Bush and chicken hawk Cheney, was formidable. They were polling 14 points ahead of Bush in ‘04.
Rove made a deal with McCain to loan him the Bushbots Nicolle Wallace, Mark Wallace and Steve Schmidt if he would not run with Kerry in 04, but rather, wait until 08.
Sure ‘nuff — McCain called Schmidt the night after the ‘06 mid terms to start his ‘08 campaign.