How did JFK and MLK impact the Civil Rights Movement?

The most significant commonality in the efforts of both JFK and MLK in terms of the modern Civil Rights Movement would have to be the passage of the Civil Rights Act. The bill had languished in the Senate for some years and was co-sponsored by Senator Kennedy, a Democrat. The Senate in the 1950s and 1960s was largely led by powerful southern Democrats who opposed integration and civil rights. This made it difficult to pass, even after JFK was elected President. After MLK led his March on Washington in August of 1963, President Kennedy went on national television to appeal to the nation for passage of the legislation. Of course, JFK was assassinated in November of 1963 and never saw the legislation passed.
JFK's successor, President Lyndon Johnson, a southerner and former senator himself, took up the cause with great fervor upon becoming president. He addressed a joint-session of congress after the "Bloody Selma" incident in 1964 to push for passage of the bill. He famously ended his speech with the words "we shall overcome." The bill passed, and MLK was present at the historic signing of the Civil Rights Act of 1964 that summer.