What is a negative ad?

Sounds like a dumb question, but let's think about that for a moment.

Does an ad become "negative" simply if it tells you why you should not vote for the opponent? If so, why is that so bad? If you listen to the media, negative ads are to be frowned upon (especially if they come from Republican candidates, but that's another blog entry entirely). Is the goal to simply spend all your time talking about yourself and your qualifications? But even if you do that, you're still saying "I've done A, B and C," with the implication being that your opponent hasn't done A, B or C, so you shouldn't vote for the opponent. If you were shopping for a new car, would you only want to know the good features of the models you're comparing - or would you like to know the flaws of each model, too?

Can you talk about the opponent at all without it being classified as "negative?" What if the things you're saying came right from the opponent's mouth? "My opponent said X, so vote for me, because I stand for Y." Lots of campaigns use comparison pieces that highlight where both sides stand on several issues. Are these by definition "negative?"

How about highlighting who endorses your opponent, or where s/he gets campaign contributions? Now you're starting to get into an eye-of-the-beholder situation. Saying that the XYZ Union endorses your opponent only gets you traction with voters who think that's bad. Your opponent cries foul, calls your piece "negative" and probably garners some support from those who think it's a great thing to have the support of the XYZ Union.

I don't want this to sound like a denial of the existence of negative ads, but I think it's safe to say that the definition of "negative" is far less objective than the media would have you believe.