roughly in the first quarter of the 20th century, between construction and the consolidation of the New Deal Coalition (the 1936 election), the African-American vote migrated from being monolithically Republican to monolithically Democratic.
Although the 1936 election was a huge turning point in this direction, Republicans still had non-trivial amounts of African-American support through the mid-1970s.
In this era where double-digit percentages of African-Americans voted for both Democrats and Republicans, were there any demographic or regional characteristics of the African-Americans who voted for one party or the other? [This is taking into consideration of course only those who *could* exercise the franchise in this period]