While Donald Trump has only been president for a little over a year and a half (it seems longer, doesn't it?), with the 2020 election starting in January of next year (assuming it hasn't started already), it is perhaps not too early to start looking at the question in the title this post, since it could happen in a little more than two years.1
In an editorial (“What has become of the Republican Party?”) and a long article (“How the elephant got its Trump”) back in April, The Economist touched on this question. One of the most interesting points in the article was that Trump supporters came to the Republican Party before President Trump did. Donald Trump didn’t create the populist wing (or whatever you want to call it) of the Republican Party. He merely took advantage of it.