Who was the last Republican to win the black vote?

[Southern Senator North Carolina Yankee]

Republican's began to collapse in the black vote in 1934 and 1936. They lost ILL-01 for instance in 1934. They came close to regaining it in 1942 I think, and it was somewhat competitive in 1946, but it has been solid Dem after that.

[Southern Senator North Carolina Yankee]

I thought black voters were a swing group during the 1952, 56, and 60 elections and was surprised to see Democrats win this demographic so handily. In my mind I imagined President Eisenhower winning a slight majority both times, and then Kennedy flipping it back with a slim margin brought on by his attractiveness as a candidate and the MLK jail phone call.

They were an important demographic. The word swing demographic implies that the group itself swings, but it can also mean that a certain threshold will swing the election.

In 1948 for instance, the states of OH, ILL and CA were pivotal and Truman won all and African-Americans provided that margin of victory. Had Dewey achieved say 35% it might have swung those states and the election.

[Southern Senator North Carolina Yankee]

You misread 1952-1956, Ike GAINED 15 points because of Brown v Board, that and Stevenson and Co. were generally very lukewarm toward civil rights and took the vote for granted. There's a reason it was precisely at that moment LBJ switched positions on Civil Rights.

It is also when a lot of the ethnic white Democratic machines in the north embraced Civil Rights as well, because they realized a coalition of middle class whites and African-Americans was a threat to their power and it had only been the loss of African-Americans that toppled Republican machines in Chicago and Philadelphia over the prior 20 years.

[Southern Senator North Carolina Yankee]

The Regan drop is probably due to his policies neglecting inner cities. Reagan also suffered a drop in the rural Midwest.

I would add to that, the likely impact of older generations of African-Americans dying off, who were Republicans by tradition and legacy, and their replacement by Baby Boomers who were Democratic because of the Civil Rights Era.

That could explain the decline from the mid teens from 1968 to 1980, to the low teens/high single digits from 1984 and onwards.