I think that McCain wants to run for the GOP nomination in 2008, and it's comments like this, among many others, that make that nomination a long shot. If (when) he loses, he'll have another tantrum like he did in 2000, and may run as a third party candidate to try to screw the GOP. However, if he runs, I think he'll draw as many votes from RATs as he does from Republicans, and may have a fairly minor effect on the outcome.
"If (when) he loses, he'll have another tantrum like he did in 2000, and may run as a third party candidate to try to screw the GOP"
I have thought this for a long time! I can see him pulling a "Perot"