There was a Sea Change in the 1960's and 70's -- under Lyndon Johnson and Richard Nixon. Since then, the shoe has been on the other foot.
Lyndon Johnson pushed for strong civil rights legislation and, once that legislation was passed, Nixon and Lee Atwater adopted a Southern Strategy. As a result, most white racists switched parties. They changed from D to R.
Nixon and Atwater told the white racists and bigots that they were welcome in the Republican Party, and most of them have found a very comfortable home there ever since.