I’ve always tried to keep a distinction between negative ads and contrast ads.

Maybe it’s a losing cause, as voters don’t seem to appreciate the difference, and if they don’t, than those of who cover politics probably shouldn’t either. But to me, an ad is “negative” when it attacks someone’s personal character. John McCain uses the Concord Monitor to call Romney a “phony.” That’s negative.

When Romney runs an arguably misleading ad that tries to draw a contrast between himself and McCain on a matter of public policy, he’s not resorting to an ad hominem attack.

But maybe I’m being too strict.

Romney’s immigration contrasts are almost willful in their ledgermain, and they seek to plant in the minds of a voter a distorted sense of what McCain says on the issue. Romney’s ad is much more cynical and manipulate than McCain’s ad; McCain just throws the “phony” label out there.

Point taken.

Continuing this conversation with myself, though, I’ve got to wonder: what about an ad that contrasts Hillary Clinton’s health care plan, which, with its mandate, would essentially insure the entire country, and Barack Obama’s health care plan, which could leave up to 15 million with insurance? This dispute is legitimate; neither side would argue that their plans are identical, and while Obama disputes the notion that his plan is inferior to Clinton’s in terms of its comprehensiveness, it doesn’t seem fair, somehow, to throw around the adjective “negative” to describe the idea of Clinton’s pointing this out.

Is there a meaningful difference? What hidden rules should we abide by? What do you think?