John Kerry is quite clear about the direction of his campaign:

After various artists had called Bush a 'cheap thug,' compared him to a criminal and made off-color jokes about his name, Kerry said, 'Every performer tonight, in their own way, either verbally or through their music, through their lyrics, have conveyed to you the heart and soul of our country.'
The next day, Kerry's campaign manager, Mary Beth Cahill, said, 'He does not approve of some of the remarks that were made last night.' But she had no answer when asked why he didn't say so at the time."

So much for a "positive" campaign...