"Guilt by association" is defined as the attribution of guilt (without proof) to individuals because the people they associate with are guilty. This leads to the "guilt by association" fallacy.
I would like to point out the opposite phenomenon, which is just as prevalent (if not more so), particularly in politics--and that is "virtue by association", which almost always leads to equally fallacious reasoning.
Most often, this virtue is transmitted by having a celebrity endorse a candidate and thereby rub off some of his presumed "virtue" onto the candidate, whether deserving or not.
The Obama campaign wants us to assume virtue by association, but decries the idea of guilt by association--even if the virtue we are to assume in Obama comes via a person he has had little to do with over the years; and the guilt comes via close personal and professional relationships he has had for decades.
If political endorsements are such a big deal, then why not also factor into one's evaluation of a candidate those endorsements by the significantly less virtuous...?
Colin Powell's endorsement of Obama counts; but Ayers', Wright's, Rezko's, Hamas', Iran's, Farrakhan's, Castro's, Chavez's, and all the other endorsements by assorted celebrity bigots, dictators, terrorist groups, and lunatics we should ignore?