The African-American movement away from the GOP took a little longer than this. Even during the 1950s, Eisenhower was averaging 40% of the black vote while making inroads in the south. Eisenhower was very conservative civil rights (to give the best example of it he considered the appointment of Earl Warren the biggest mistake he ever made) but his administration, led by Herbert Brownell did make some efforts towards civil rights in a way they hadn't before. I think that's why Robinson was willing to back GOP candidates to that point (he actually campaigned for Nixon in 1960 and he worked for Rockefeller when he was governor.) Of course, he eventually realized just how badly he had been used by the GOP, perhaps well before thIS INCIDENT.

I knew about Rockefeller's speech because its the opening pages in his recent biography. Rockefeller was a great man who could have been a great President. But like so many politicians, he had horrible timing becoming active in the party when it started to radically move away from him. I don't know if he ever had a realistic chance of winning the 1964 nomination even before Kennedy was killed. But the world was a poorer place when the GOP rejected the Republicanism he stood for. (Of course, things might not have been much better. Rockefeller's campaign adviser in 1964 was a man named Henry Kissinger. )