The story of JFK winning the black vote and the election because of the decision to call Coretta Scott King on the occasion of MLK’s unjustified arrest could use a little complication. Northern blacks started voting Democratic during FDR’s time and were an important source of support for Harry Truman’s re-election bid in 1948. But in 1952, the Democrats put Alabama’s John Sparkman on the bottom of the ticket, and Ike picked up a bigger share of the black vote than Republicans had been getting recently. In 1956, Eisenhower got Adam Clayton Powell, Jr.’s endorsement and his share of the black vote went up further still to something in the neighborhood of parity.
The second Eisenhower administration featured a couple of high-profile fights on civil rights in which Eisenhower, Nixon, Kennedy, and Lyndon Johnson were all playing slightly murky roles with everyone trying to play to incompatible audiences all simultaneously. But the stage had, in essence, been set for the GOP to make a strong play for regaining the loyalty of black voters — they’d been making electoral inroads, the Eisenhower years had witnessed more progress on civil rights than any administration since LIncoln, and the Democrats were once again “ticket balancing” with a southern vice president. The 1960 election wound up not playing out that way, and then by 1964-65 the Johnson administration secured a civil rights record that left anything the Republicans had ever done in the dust.