http://www.politicususa.com/fox-news-march-ratings/ an anti-Fox source, but I don't doubt their statistics.
What appears in the TV news, Fox or otherwise, isn't the same as the totality. People like Miggs, if I'm not mistaken, are convinced beyond dissuasion that the totality of the mainstream media - TV News as well as Mad Men and probably Judge Judy and sports coverage and WAY TOO MUCH of Fox - are advancing a leftwingified super-plot to annihilate or transform all that's good and holy and bury it in the Gulag. They're right, but just don't realize that what they have in mind is much worse, and that neither is much going anywhere anyway.
FNC didn't emerge from the vacuum. It filled a growing niche for its product that could be described in different ways, for instance as a provisional perspective at a particular intersection of power and culture. I read somewhere BTW that Fox's viewership is in major decline, but maybe it was a one-month blip - had been meaning to look look into it further.