On Wednesday night, eight Republican presidential candidates gathered in Milwaukee for the first GOP primary debate. There was a lot on the line for each of them. But there was also an enormous amount at stake for the news organization that hosted the debate: Fox News. Consider the cross currents that the two Fox moderators, Martha McCallum and Bret Baier, had to deal with: First there was Trump, who refused to participate and lashed out at Fox and its talent, including Baier, on social media. Then there was Tucker Carlson, McCallum and Baier’s former star colleague who is in messy litigation with the network, and who nabbed Trump for himself and counter-programmed the evening with an interview that aired simultaneously with the Fox debate. Then there was Rupert Murdoch hovering in the background. In the days before the debate there were new reports that the man who runs Fox, MacCallum and Baier’s boss, has his own strong feelings about who the GOP nominee should be. If th...