The signing of the Civil and Voting Rights Act by LBJ was the lynch pin (no pun intended) in Southern Democrats leaving the Democratic Party.
Up through 1970, the Southern Democrats were still active in subjugating the constitutional protections of minorities in the south and at various points the President had to enforce constitutional protections by calling in Armed Forces to protect American citizens residing in the region.
<quoted text>Confederate states were the Democrats.
Southern Democrats are members of the U.S. Democratic Party who reside in the American South.
In the 19th century, Southern Democrats comprised whites in the South who believed in Jacksonian democracy. In the 1850s they held that slavery was a good thing and promoted its expansion into the West. After Reconstruction ended in the late 1870s they controlled all the Southern states and disfranchised the blacks (who were Republicans). The "Solid South" gave nearly all its electoral votes to Democrats in presidential elections. Republicans seldom were elected to office outside some mountain districts.