In the early 1800s, they were the definitive pro-slavery wing of the party, opposed to both the anti-slavery Republicans (GOP) and the more liberal Northern Democrats. After losing control of their party and territory in the American Civil War, and during the Republican-led Reconstruction that followed, Southern Democrats regrouped into various vigilante organizations such as the Ku Klux Klan and the White League.
Eventually "Redemption" was finalized in the Compromise of 1877 and the Redeemers gained control throughout the South. As the New Deal began to liberalize Democrats as a whole, Southern Democrats largely stayed as conservative as they had always been, with some even breaking off to form farther right-wing splinters like the Dixiecrats. After the Civil Rights Movement successfully challenged the Jim Crow laws and other forms of institutionalized racism, and after the Democrats as a whole came to symbolize the mainstream left of the United States, the form, if not the content, of Southern Democratic politics began to change. At that point, most Southern Democrats defected to the Republican Party, and helped accelerate the latter's transformation into a more conservative organization