Jane Mayer reports in The New Yorker:
Trump has made the debate a point of pride. He recently boasted to the Times that he’d won it despite being a novice, and despite the “crazy Megyn Kelly question.” Fox, however, may have given Trump a little help. A pair of Fox insiders and a source close to Trump believe that Ailes informed the Trump campaign about Kelly’s question. Two of those sources say that they know of the tipoff from a purported eyewitness. In addition, a former Trump campaign aide says that a Fox contact gave him advance notice of a different debate question, which asked the candidates whether they would support the Republican nominee, regardless of who won. The former aide says that the heads-up was passed on to Trump, who was the only candidate who said that he wouldn’t automatically support the Party’s nominee—a position that burnished his image as an outsider.
Of course they colluded.