Tacitus has written a good essay on the role of race in both the Republicans and the Democrats. Choice quote:

Of course some Republicans and some conservatives are racists. From the moment that Barry Goldwater -- a Jew without a racist bone in his body -- decided to stand on principle for the ideal of free association, the racists of the South knew they had a socially acceptable and morally justifiable cover for their loathesome proclivities. And so the "Southern strategy" was born, and so the old Confederacy was won for the Republican Party. (And so, in sick counterpoise, was the Democratic Party made the natural home for the nonwhite racists of America.) Is this a badge of shame -- the original sin of the modern Republican movement?