Dateline the Nineteen Sixties, not the Ken Burns version
A magnet for controversy during his nearly half-century Senate career, Strom Thurmond switched parties in 1964, primarily because of his vehement opposition to the Civil Rights Act of 1964, and endorsed Republican presidential candidate Barry Goldwater. In the months before switching, he had “been critical of the Democratic Administration for … enactment of the Civil Rights Law,” while Goldwater boasted of his opposition to the Civil Rights Act.
New York Times, Sept. 16, 1964.