Can anyone explain McCain's support of W?

McCain called on the Kerry campaign to cease and desist using the ad that has McCain himself telling Bush (during the 2000 Republican primary) that he should be ashamed for his methods of using Vietnam vets to sully the record of himself and other candidates who served - and you can feel how cornered in his own bullshit Bush suddenly feels. And you can tell at that moment that this is not political BS - McCain is feeling it, and Bush is feeling it. This absolutely justified contempt is a very real thing. Which brings me back to the same old question: why does McCain support Bush? The way he supports the Clown-in-Chief escapes me, as much as it escapes everyone who knows the history between the two men, when he's so clearly been screwed over by Bush & Co in numerous ways. "If I were a conspiracy theorist", I'd suggest that they brought him into a little room at some point and "explained the situation", that if he messes around with the big boys, it's not just him, it's his family too. It was McCain himself who, a few months ago in response to a reporter question about how the Republicans could get his support on a budget he refused to approve, said, "I could suddenly die in a horrible car accident". My brother, more sensible, says it's just that McCain hasn't ruled out running for the Presidency again in 2008 and needs to show his creds as a party player. But it's still disheartening and sad - unless of course you're a Republican ready and willing to suck down the sewage of the current smear campaign.