Years ago that expression was developed to make the point that the media often creates a drumbeat that leads to war. William Randolop Hearst reportedly told a photographer before Spanish-American War, "You give me the pictures, and I'll give you the war."
If the "Dog" is our country and people, and the media are the tail, then we should be controlling the function of the media to provide us with true information, as a dog controls the wagging of its tail. If the "tail" of the media is controlling the "dog," then the dog is out of control and can be led into any fiasco.
While listening to Thom's show today, it occurred to me that today's "Wag the Dog" scenario is that the media is giving us a President that benefits them financially, but harms the country and the people, and they know that.
We need to take back control by not lending our "eyeballs" to their "infotainment," but rather seeking out media sources and groups that provide truthful information. Americans need to start thinking about the information they need to make good political decisions. Let us not be led like dogs into the fiasco that is Donald Trump.