The original meaning of the slang term scumbag was a bit more specific than "despicable person" -- it meant "used condom." The New York Times once put a scumbag in its famous crossword puzzle and angered readers.
Former Rep. Dan Burton called President Clinton a scumbag in 1998, sparking press attention in the word's unsavory origins.
Now that I've told you this, please enjoy the following metaphor from Dennis Byrne's commentary about the Foley scandal in the conservative weekly Human Events Online:
... for Rush [Limbaugh], it appears to be just one more case of defending the castle against another onslaught from the left. In this, he's not doing Republicans and conservatives any favors. It just gives gleeful Democrats an example of Republican "hypocrisy." Of how Republicans keep talking about America losing its moral compass, while they've lost it themselves.
Democrats are making gains with it, because it is becoming increasingly true. Otherwise it wouldn't have taken Republicans so long to admit that they messed up by not smelling the scumbag in their midst.