The Democrats have meanwhile distanced themselves from lyrics by supporter and rapper Ludacris, which brag about an Obama presidency being destiny, call President Bush "mentally handicapped" and say Mr McCain doesn't belong "in any chair unless he is paralysed".
Mr McCain's campaign manager said it was up to the American people to decide what was positive or negative.
"I'm going to do everything in my power to protect my candidate and to define the race in terms that I think are appropriate," said Rick Davis.
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