I'm no defender and his seeming desire to vote against Bush on high visibility issues ticks me off. But, he is still far more conservative than any Democrat Senator and many Republicans.
His recent voting record still gets him a conservative rating in the high 70's or low 80's. That puts him in the middle of the pack with many other Republicans. Compared to Jeffords with a rating of 27, McCain is conservative. Don't expect him to join Jeffors in his stupidity.
McCains biggest problem, in my opinion is that he lets his jealousy of Bush drive his votes.