Here is an interesting overview of false advertising claims. It is specific to politics, but relevant for all kinds of advertising. Revolutionary!
It is illegal to make false claims in a TV or radio commercial unless you are running for political office. If you’re selling toothpaste, your claims must be vetted by legal and medical professionals. But not if you’re selling a candidate.
If you’re selling a candidate, not only can you lie about his or her record, but also and more to the point, you can lie about his opponent.