“The black vote did not become as monolithically Democrat as it had been (pre-New Deal) monolithically Republican until 1964.”
“Why do you say that, do you have numbers for the years before 1932?”
No, I don’t have actual numbers before 1932, but if (as per the numbers you provided) the GOP nominee got between 25% and 39% of the black vote between 1936 and 1960, and FDR got only 23% of the black vote in 1932 while getting a far bigger percentage of the national popular vote than any Democrat in the prior 65 years, I am quite confident that none of Al Smith, John W. Davis, the racist Woodrow Wilson (who fired all blacks from federal civil service jobs), William Jennings Bryan, Alton Parker, Grover Cleveland, Winfield Scott Hancock, Samuel Tilden, Horace Greeley or Horatio Seymour got as much as 20% of the black vote in the elections between 1868 and 1928.