Blacks had always been Republican and were in 1932, Blacks reversed their vote in the 1936 election when they suddenly and mysteriously switched with 71% for FDR, it has been Democrat since then.
As I recall Blacks were voting about 75%-25% against the GOP in the 1960’s.
My point was more along the line that a new and stunning level of undisguised Black anger and contempt for the GOP emerged around 1968.
Race was no longer the issue.
It was now an issue of deeply held political values.