John Oliver said in his last Sunday show (12th February) that he paid several TV channels to broadcast an advertisement obviously making fun of Mr Trump (around 21:40, toward the end of the video). The message is to be sent as a commercial advertisement. One of the channels concerned was Fox News, which he picked so that Mr Trump was likely to see it. However, I am not sure that this kind of message would be approved by the staff of Fox News.
Has this kind of thing been done before?
On what legal basis (if any) could Fox News refuse to broadcast the advertisement?
I would be interested in an example of a similar action, using commercial advertising to send a political message on a channel known to be opposed to this particular message. I cannot think of one. There is mandatory equal time granted for each candidate in some countries during the presidential campaign, but it isn't really the same thing.
Edit : Can someone show if the ad was actually aired, and if so on which channel?