The left has made a huge mistake by assuming that liberal idea must be true because they come from bright people. Bright people can, and often do, have terrible ideas.
The problem is not unique to the Republicans. The challenge of buying into climate denial, voodoo economics, creationism must be daunting ..even if it were not flavored by racism. Dems just have to buy into protectionism, teacher unions, and racial favoritism.
The question is hoe can a bright person do this? How does someone like McCain justify his choice of Sarah Palin? What would Bill Buckley say about climate denial?
FWIW, I think Cruz, Walker, McCain, Jindahl, James Baker, Bill Buckley, Disraeli, Taft, … all of these Republicans are or were bright. However, all ambitious politicians share a conviction that their own ideas are so important that is OK to buy into the rest of the platform. Their intellectual skills (sophistry) allow bright politicians to create a semblance of an intellectual whole.
An intellectual whole requires an effort much like the effort a method actor uses to get into a part. Creating that intellectual whole must be the the easy part, to be convincing, a politician needs to believe in what he or she says.
This method acting fits naturally with our partisan, two party system. There is no consistency of ideas in either party. Liberal/Dem policies are heavily biased toward unions and minority ethnic groups. Tea Party/Rep policies are a weird collage of racists and big business interests. For either team, being a player means fitting into your part .. believing in the party line!
A good friend once explained Ronald Reagan to me. I asked how could the public be deceived by this stupid man? My friend, an actor, explained that Mr, Reagan was playing a role.