As I noted months ago, the GOP establishment was appalled by Trump, and, even worse, thought he would lose. As a result, they treated him, not as a real Republican, but as a de facto third party candidate with whom they had a temporary tactical alliance. In this way, they thought they could limit the damage to their brand after the inevitable Clinton landslide.
Today, of course, the shoe is on the other foot; Trump is a free agent relative to the establishment. Will he quietly renounce his idiosyncratic positions on trade, entitlement spending, and foreign policy and become a mainstream Republican, or will he make overtures to the Democrats on selected issues in order to maintain his freedom of action and keep his favorability ratings up? I’m guessing the latter, and the Democrats will have to decide how to respond on an issue-by-issue basis.