They went from their traditional GOP vote of about 70% in 1932, to an instant reversal of about 70% democrat in 1936, and have maintained their perfect democrat vote since, just as they maintained their perfect GOP vote before 1936.
Ingrates.
Both my mother's and father's ancestors (all four sides) fought to free them and we've been Republicans since Lincoln. If the Republican Central Committee had any 'ovnayim it would sue every Democrat who lies that "all those Republicans became Democrats and all the old Democrats became Republicans."
I'm a "religious fanatic," and there are no Dixiecrats in my woodpile that I know of.
This instant and permanent reversal is unique and unexplained, it must have taken a massive and historically effective publicity push promoting an offer of some type to pull it off, yet none of us knows the details of what the democrats did to take FDR from the normal black support of 23% in 1932, which was a typical presidential election vote for them, to his suddenly winning 71% of their support in 1936, and it never reverting back to the GOP.
Something huge happened, “huge”, yet we don’t know what it was or how it reached the entire black population so quickly and effectively.