If McCain votes against his leadership, whatever remote possibility he had of garnering the 2008 GOP nomination is over. I suspect he'll change his mind again.
Hmmmm... there are a couple of good arguments for McPain to vote with the demonRATS! Either: (1)We won't have to worry about him in 08 or (2)We'll have the votes for the Constitutional option! It's more likely a win-win for us, however the fool votes.