I've gotta agree. The primary rule of any struggle is to not underestimate the opposition. The Democrats certainly underestimated Trump, actually convincing themselves that he is an inept idiot and they are master strategists. The sad part is that they still are underestimating him. Trump is no fool but they can't admit that he has outsmarted them at every turn and still is doing it primarily because they can't get over believing that anyone who disagrees with them is a fool.Sounds pretty accurate, given what happened.
They didnt undersestimate Trump (who, by the way, is clearly is a fool) but the impact he made.