Why Did the South Turn Republican?

According to the usual claim by the Enlightened Ones, it's because the Republicans sold out and started using racist “code words.” (By the way, is the term “code words” a couple of code words?) Matthew Yglesias (seen via Megan McArdle) offers a slightly different theory, that the Democrats became less racist:

The dam began to crack with Harry Truman, and then under Lyndon Johnson the national party decisively broke with this corrupt bargain. With that done, white southerners just took their conservative views on taxes and national security into the Republican Party where such views belonged. Racism is a key part of the story, but it plays a much bigger role in explaining why Adlai Stevenson and John Kennedy won South Carolina than in explaining why Ronald Reagan and George W. Bush won there.

This theory ran into lots of opposition in the comments. Some of the comments consisted of repeating the standard theory loudly and slowly, but others actually brought up a fact or two. For example, the South of a century ago was strongly anti-capitalist. (We still see some of that in the preposterous decisions of Southern juries.)

My theory, for whatever it's worth, is that White Southerners spent a century telling each other that they weren't really racist, they were just defending themselves and property rights against liberal/communist agitators. After a century of that, their pretenses had become real. I'm reminded of a well-known quote from Mother Night by Kurt Vonnegut:

We are what we pretend to be, so we must be careful about what we pretend to be.