It's easily the most useful diagram I've found for understanding the practice of journalism in the United States, and the hidden politics of that practice. You can draw it by hand right now. Take a sheet of paper and make a big circle in the middle. In the center of that circle draw a smaller one to create a doughnut shape. Label the doughnut hole "sphere of consensus." Call the middle region "sphere of legitimate debate," and the outer region "sphere of deviance."
That's the entire model. Now you have a way to understand why it's so unproductive to argue with journalists about the deep politics of their work. They don't know about this freakin' diagram! Here it is in its original form, from the 1986 book The Uncensored War by press scholar Daniel C. Hallin. Hallin felt he needed something more supple--and truthful--than calcified notions like objectivity and "opinions are confined to the editorial page." So he came up with this diagram.
Let's look more carefully at his three regions.
1.) The sphere of legitimate debate is the one journalists recognize as real, normal, everyday terrain. They think of their work as taking place almost exclusively within this space. (It doesn't, but they think so.) Hallin: "This is the region of electoral contests and legislative debates, of issues recognized as such by the major established actors of the American political process."
Here the two-party system reigns, and the news agenda is what the people in power are likely to have on their agenda. Perhaps the purest expression of this sphere is Washington Week on PBS, where journalists discuss what the two-party system defines as "the issues." Objectivity and balance are "the supreme journalistic virtues" for the panelists on Washington Week because when there is legitimate debate it's hard to know where the truth lies. There are risks in saying that truth lies with one faction in the debate, as against another-- even when it does. He said, she said journalism is like the bad seed of this sphere, but also a logical outcome of it.
http://www.huffingtonpost.com/jay-rosen/audience-atomization-over_b_157807.html