From Jonathan Bernstein:
Understanding how a president thinks can help make sense of his decisions. Trump’s case is harder than most.
The reporting is pretty clear: Trump doesn’t read briefings, on politics or anything else. He doesn’t appear to have absorbed the basics of public policy, whether on health care or national security or even issues, like trade, that he cares about. Instead, he seems to pick up fragments of information in conversation or, more often, from cable television. Often, it’s partisan talking points, which isn’t surprising since much of what airs on Fox News, CNN and MSNBC consists of partisan talking points. Trump then extracts some fact or detail he finds useful from that input, and comes up with his own way of expressing it. Usually, he pretties it up, smooths out any nuances and exaggerates significantly. Then he tests it out, on Twitter and especially at his rallies, working for the wording that gets the biggest reaction. And then? As far as I can tell, Trump winds up believing the final version of whatever it is he has produced.