From the mid-late 1930's through the end of WWII, black votes were around 50-50. Post WWII, Truman (somewhat starting with the military).... I'll copy and paste a paragraph from Wapo

"In 1948, as Real Clear Politics' Jay Cost wrote a few years ago, Democrat Harry Truman made an explicit appeal for new civil rights measures from Congress, including voter protections, a federal ban on lynching and bolstering existing civil rights laws. That year, the number of blacks identifying as Democrats increased."

These rather tepid steps made to a degree in response to the large number of black veterans in WW2, changed the black electorate to something like 60-40 black votes for Dems. It started a trend that accelerated the trend toward Dems. The Kennedy family helped MLK, whose family may or may not have been Republicans (seems like some conflicted reporting) with some of his legal problems including Robert's work to get him out of the Birmingham jail. Of course the Civil Rights Act, passed over the strong objections of the Southern Dems, solidified that vote. African Americans have voted well over 80 percent for the Dem candidate in every election after 1964.

Of course, Nixon courted those same southern Dems pretty hard in his 1968 race and modernized the party realignment. I think you have to really put your head in the sand not to understand that of the 70 percent white vote of rural Southern Whites going to Republicans weren't once in families aligned with those Dems.

And by you....I didn't mean you necessarily.