First off, the South left the republican party after the civil war because they would not be part of the "party of Lincoln". That didn't mean that they became liberal Democrats, but were still the racists that became republicans after the civil rights and voter rights legislation of President Johnson.
Second the south wasn't solid Democratic before the civil war. You pretend to be on the side of the marchers in Selma Al, but you aren't fooling anybody.
You must have been home schooled or dropped out of school before Civics class in eighth grade.