Perhaps the anti-intellectualism has driven some of the brighter people from the Party. I've never seen a study on it.
Anti-intellectualism, as you know, has deep roots in American politics, religion, and culture -- ever since the early 1800s, at the least. It seems to have roots in the Cavalier culture from England that mainly settled and shaped the American South, but Tocqueville felt it was also a natural outgrowth of democracy itself. It's infection of the Republican Party is a more or less recent development -- since the 1970s. Prior to that, the Republicans were the 'intellectual party' and the Democrats were the 'anti-intellectual party'. Apparently, it arrived in the Republican Party via the Evangelicals. It might be noted that the Evangelicals -- in so far as they are related to the Fundamentalists -- got their start as an explicitly anti-intellectual movement. The intellectuals the Fundamentalists were reacting to were the German philologists of the late 1700s and early 1800s. The philologists were busy putting their scholarly tools to the task of analyzing the Bible. They were making discovery after discovery that did not jive well with the King James translation, nor with much of the theology that had been based on the translation. Naturally, humans being humans, one of the responses to those discoveries was to turn anti-intellectual.
Does any of that help?
Some interesting tidbits for me to go and research.
Thank-you sir.
(I'm aware really only of post 1900 anti-intellectualism in the US, and even then only in certain contexts)