Which tells me -- and could tell you, it's not a damn secret --- that the Liberal goals of the original Republican party were pushed off the table when it gravitated to the interests of the rich and the corporations a century ago; see especially "McKinley, William" when you break down and crack a book. Simultaneously the DP was absorbing a growing opposition Populist movement, which is what attracted blacks as well as .... Jews... Catholics... immigrants... women... any group that's been marginalized.
Know what's essential about history? It tells you where you are now, by explaining where you came from.
And I've already posted the stats and charts on the black vote, and then the black voters, migrating from the RP to the DP beginning in the 1930s.
"Civil rights", depending on what that means, have been passed by both parties. Partisan hack.