Political Advertising - Who Is Accountable?

John McCain just dropped a fresh ad on America's carpet. But while the substance is doo doo, the style is more like a rich, dark chocolate mousse - with imported 80% cacao. Deep, ominous strings crescendo as flashy images dash across our retinas. This is powerful stuff - designed by trained professionals to move the viewer at a subconscious level. The more sucessful it becomes, the more it begs the question:

Who are the writers, producers, and agencies behind political ads, and when, if ever, should anyone hold them responsible for the content, and the impact of their work?

In most cases, these artists and technicians are merely 'guns for hire'. After all, it is the cigarette companies who were ultimately held accountable for their misleading advertising, not the agencies, or actors like Ronald Reagan who made the ads. But could we imagine a scenario where an ad is so offensive or dangerous that some liability spills over onto the people who actually made it? After all, we don't let the hit man go free, just because he was 'just doing it for money'...