You do know that Democrats still basically held the South until 1994 (and remained powerful past 2000), right? Over a generation after the segregation ended and well after views on race had changed.
Are you saying the GOP party today is the same one during Lincoln time. No there was not big switch that happen between the parties but a gradual one that happen over decades and basically its more regional then party stances. The party started to change when its leaders started to cater to that good old southern vote. You only have to look at the voting throughout the years and how it has changed over the decades to see exactly how things have changed between the Dems and GOP especially when the Dems started to embrace more civil rights agendas Actually, this is during the time when most black Americans started to leave the GOP party because the GOP started to cater to more white southern voters by voting against civil rights.