Truth is the only major dem politician to switch was Lester Maddox. All the rest of 'em stayed democrats.
The south did start changing to a two party system - but it was later. Started slowly with strong migration from the North. My mother - who had been a Republican in the north - switched to being a democrat in the 50's South because there was only one party in the South. If you wanted a voice, you had to be a democrat in the South. When enough people moved South to form a Republican party that could win an election or two, my mother - and many like her - switched back to Republican.
The one and only totally racist party in the South was Democrat. Democrats were the KKK, the White Citizens Council and the Sheriffs that kept blacks in line. George Wallace in the school house door, Robert KKK Byrd - powerful Senate leader, Bull Conner with his water hoses, Gov Hollings with his Civil War Battle flag trotted out in the 60's to stick it to civil rights protesters - they were all democrats.