It’s not comparable at all. Democrats were literally the party of slavery. Then Roosevelt came along with The New Deal, pushing them to the left. Then the civil rights movement began, and the “Dixiecrats” (racist southern Democrats) had enough and left the party over it.

Racist, anti-integrationist Dixiecrats like Strom Thurmond remained hardcore Republicans until the day they died.

The “Democrats” that created the KKK are the basis for the modern Republican party.