Anecdotally, from Wikipedia:
Legend has it that, as he put down his pen, Johnson told an aide, "We have lost the South for a generation", anticipating a coming backlash from Southern whites against Johnson's Democratic Party.
Emphasized because President Johnson was a Democrat bemoaning the fact that a lot of racial bigots were going to flee a party that passed the 1964 Civil Rights Act.
And if the bigoted idiots fled, as predicted, from Johnson's party, can anyone figure out where they went to?
Anyone?
Anyone?
Bueller?