FDR hooked alot of people with his gimme “programs”.
(I despise the SOB.)
Blacks moved Dem because of it, but they solidified in the ‘60s when the final nail of open welfare and “AA” (ha ha) came in.
The sole Black member of Congress (who served from 1929-1935) was Chicago’s Oscar DePriest. DePriest was no left-winger and bitterly opposed the New Deal and its “goodies” because he was utterly terrified it would destroy the industriousness and independence of the Black community. That made him an enormous target for the 1934 midterms for FDR to get rid of him. The formerly White Republicans in the district voted overwhelmingly for a Black Democrat (himself a former Republican) overwhelmingly and DePriest lost (despite his apparently still receiving a majority of the Black vote, but not enough of them).
The district (IL-1) still remained competitive for Republicans until the 1946 elections (with the GOP nearly winning the seat back a few times - although Chicago Democrat corruption was likely to blame for that not happening). Sadly, after 1948, the district, like Chicago, became heavily polarized and Democrat and never was to elect a Republican again. DePriest’s greatest fears came true.