mainly macro: Trump: Misleading the People:
The story is in fact told better than I ever could by Bruce Bartlett, who worked in the Reagan White House and for George HW Bush, so I’ll just summarise it here. The story starts under Reagan, who provided pressure to withdraw the Fairness Doctrine, which was similar to what keeps UK broadcasters from being partisan. Initially that allowed the rise of talk radio, and then Fox News. Gradually being partisan at Fox meant misinforming its viewers, such that Fox viewers are clearly less well informed than viewers of other news providers. One analysis suggested over half of the facts stated on Fox are untrue: UK readers may well remember them reporting that Birmingham was a no-go area for non-Muslims.
But why is this causal, rather than simply being a mirror on the rightward drift of the Republican base? The first point is that there is clear evidence that watching Fox news is more likely to make you vote Republican. The second is that, like the tabloids in the UK, this propaganda machine can turn on party leaders and keep them from moving left. The third is that it is also a machine for keeping the base angry and fired up and believing that nothing could be worse than voting for a Democrat. It is Fox News that stops Republican voters seeing that they are voting for a demagogue, conceals that he lies openly all the time, incites hatred against other religions and ethnic groups, and makes its viewers believe that Clinton deserves to be locked up. Just as UKIP (and perhaps now the Conservative party) is the political wing of the tabloids, so Trump is a creature of Fox news.