As we celebrate Martin Luther King Jr. Day, here’s a largely forgotten story about how an almost random phone call, to King’s wife Coretta Scott King from John F. Kennedy, played a huge role in shifting national black voting habits from Republicans to Democrats.

Most people think the major shift occurred in 1964 as a result of Republican presidential nominee Barry Goldwater voting against the Civil Rights Act over a constitutional objection to one of its provisions. And, yes, the reaction against Goldwater accelerated the trend and made it well-nigh irreversible. But, the Kennedy incident four years earlier got the ball rolling.