I don’t believe that the “18%” are all stupid. Many of that group are among our smartest citizens regarding topics other than politics. They are in a predicament whereby they would have to admit that they have been wrong about virtually everything political since the dawn of the Twentieth Century. Their vanity (or hubris) will not permit such soul-searching.
You would be surprised. During Thanksgiving dinner I had some lefties I just met say that the country was being racist against zero. My reply was if he was a CEO of a mjor company he would have been fired after his first two years. They had no comeback for that one.