Northern Blacks became majority Democrat by 1936 (Hoover got a majority of the Black vote in 1932). Southern Blacks, except for small numbers, couldn’t vote. Had they been able to vote in the numbers they do today, the Southern states would’ve sent Black Republicans to office at the legislative and federal levels.
Southern Blacks, once enfranchised, moved into the Democrat camp post-1964 (although there were some exceptions - in Birmingham, for example, a coalition of White Republicans and Blacks helped to dump the racist Democrat machine and vote in a White Republican Mayor in 1967). Unfortunately, however, Blacks became extraordinarily polarized and radicalized by 1968. No matter how much Republicans targeted policies designed to help them, they would vote Democrat in uniform lock-step regardless of their locale.
One Republican Governor in Delaware complained he spent 4 years bending over backwards to Blacks in his state, and they still voted for his old-line racist Southern Democrat opponent in 1972 (with Joe Biden being next down the ballot, where they similarly turned out both the GOP Governor and Senator). Nixon did enormous things for the Black community, as Dinesh D’Souza pointed out, but it barely earned him a couple points (around a paltry 10-12%) better than he got in 1968, and far below the 25-30% he got in 1960. So radicalized were Blacks that when poor Sammy Davis, Jr. got up to endorse Nixon in ‘72, he was turned into an instant pariah by his own community, to Davis’s utter disbelief. Anybody Black not on the Democrat plantation by 1972 had to be destroyed, and so it still remains 46 years hence.
Unfortunately for blacks, most of the jobs went to white workers, especially in the South where Democrats ruled blacks by terror.
Forget Blacks. GOP should go after Asian-Americans. GOP will remain a force in national politics even if Whites’ percentage of American Population continued decline with increasing Asian-American support. They tend to be industrious small business owners so they will be a natural fit for GOP. Just my two cents.