A total of 21 Democrats in the Senate opposed the Civil Rights Act. Only one of them, "Dixiecrat" Strom Thurmond, ever became a Republican. The rest, including Al Gore, Sr. and Robert Byrd--a former Exalted Cyclops in the Ku Klux Klan--remained Democrats until the day they died.

Moreover, as those 20 lifelong Democrats retired, their Senate seats remained in Democrat hands for several decades afterwards. So too did the overwhelming majority of the House seats in the South until 1994, when a Republican wave election swept the GOP into control of the House for the first time since 1952. 1994 was also the first time Republicans ever held a majority of House seats in the South--a full 30 years after the passage of the Civil Rights Act.

From there, Republicans gradually built their support in the South until two more wave elections in 2010 and 2014 gave them the overwhelming majorities they enjoy today.

If this was a sudden "switch" to the Republican Party for the old Democrat segregationists, it sure took a long time to happen.