How did Franklin D. Roosevelt's New Deal coalition affect African American voting patterns?
For the first time ever, most Blacks voted Democratic.
In the years leading up to the Civil War, The Democratic Party was the party of Southern planters and the Republicans were the party of Northern abolitionists. FDR brought Black voters into the Democratic Party en masse and William Howard Taft brought Northern business interests into the Republican Party. The Democrats had a conservative wing, the Dixiecrats, which endured the 1960s and 70s but pretty much died with George Wallace.
The two parties--functionally the only two since 1860-- flipped roles in the early 20th Century, and may well be on the path to flipping roles again during this election cycle. To the extent that either party ever stood for any specific principles, it's a bit muddled at this point which party holds which principles. The Republicans are nominally conservative, anti-tax, pro-small government and pro-business, and the Democrats are nominally liberal, pro-choice and pro-labor, but in practice both parties are compromised to the breaking point.