Some Southern Conservatism began to emerge in the 1938 Elections. It took a good deal of time to develop. And it was not mainly about Segregation, that is a leftist lie.
The South has always favored decentralized power, a balanced budget and a limited government. That goes all the way back to the time that they were colonies. That's not something new that emerged in 1938. It had always been there. That's what caused the South's break with the Democrat party. They became the party of big government, centralized power and socialism all of which were anathema to Southerners.