Until 1936 republicans always won the black vote. In 1932 Roosevelt got 23% of the black vote, in 1936 the switch was made, and it was permanent, in 1936 Roosevelt got 71% of the black vote while the GOP got the 28%, a complete and instant, and permanent reversal.
The democrat presidential candidates never had to sweat the black vote again.
If we could get 28% of the Black vote today we’d never lose.