You have to wonder if McCain wants to be President. If he does, he’s going to have to throw everything there is at Obama (or his surrogates do). If he’d rather be “clean” than President, he’ll get his wish.
Oh, I believe he wants it. It's just that he, like Dole, has been so insulated in Congressional Republican gamesmanship over the past decades he's not prepared (IMO) for the type of campaign the Democrats will bring to the table. Time will tell.
I expect - once Obama defeats Hillary - that McCain will get as mean and nasty (McNasty) as he is known for.
But right now, he is in cruise control. Content to let Nobama and Hillary rip themselves to pieces.
But when Obama is clearly his opponent.... then McCain will scorch the earth.