You really should read the stuff you link to if you intend to rely upon it:
“What most likely happened, I think, is that Kerry did approach McCain over a period of time, both about switching parties and about running as Kerry’s Vice President. McCain says he never took the offers seriously, and my guess is that’s true.
What hurts McCain is that over a period of time, leading Democrats who knew him reasonably well thought that he was someone who might switch parties or run on a ticket with John Kerry. Those aren’t good things to be believed, even wrongly, of a man who wants the Republican Presidential nomination.
In McCain’s defense, I suspect that these overtures reflect the Democrats’ basic lack of seriousness about policy. For the Democrats, everything is about politics. So if they perceived that McCain was angry at President Bush, they apparently didn’t consider his pro-war, pro-life, free-trade, small government views to be much of a problem. McCain, on the other hand, is serious about policy, and he seems to have understood how ridiculous it would be for him to share a ticket with a liberal like Kerry.”
McCain scoffed at Kerry because Kerry offered him the responsibility for National Defense, and McCain flatly said that the CINC does not work that way.