Many Southerners are registered Democrats but vote Republican. They will even tell you they are Democrats even though they do not vote as Democrats and share none of the Party’s ideas. The reason is family. Their daddy and their grandaddies were Democrats going back generations so they remain Democrats, although often in name only.
Remember Republicans were reviled in the South from at least Lincoln onward and Roosevelt was seen as the savior of the Great Depression.
My own grandmother would say she was a proud Democrat and when asked why would launch into near worship for Roosevelt. Nothing could change her mind. He hung the moon for her and many of my grandparents’ and my parents’ generations.