Strom Thurmond and Lester Maddox were the two racist democrats who became Republican. The other 8,000 racist demmocrat officeholders in the South stayed Democrat.
Many local officials in the South like state legislators were Democrats in their youth and or made the party switch as elected officials in places like Southern state legislatures.
In the last 50 years there have been many party switches all across the Old Confederacy from Texas where Rick Perry was once a Dem all the way across to Virginia.