The Democrats then took over in every Southern state, creating the Solid South and enacting the Jim Crow laws.
By 1964 the charge for civil rights was lead by Democrats and the opposition was lead by Democrats. The Republican Senate Leader, Everett Dirksen negotiated some tweaks with the floor manager, Hubert Humphrey, and brought his caucus over to supporting the bill. A higher percentage of the Republican caucuses in the Senate and House supported the bill than the Democrat caucuses.
Everyone knew that after FDR put together the New Deal coalition that held Congress from 1932 that they only way to end segregation would be if and when the Democrats decided to do it.
And it's a myth that the segregationists then came over to the Republican Party. The party that more strongly supported civil rights than the Democrats? Seriously? That makes no sense.
Almost no Democrat politicians switched parties after the vote. Being politicians, they just switched sides and started courting the black vote.
Liberals can't face up to the real reason Democrats switched to the Republicans. It's because the McGovernite, isolationist and appeasement wing of the party took over in 1968-1972. The cold warriors and fiscally responsible people, which most Southerners are, were pushed out by the far left.
The only one who did change parties was former dixiecrat Strom Thurmond. BUT He publicly denounced the dixiecrat platform and became a champion of civil rights unlike al gore sr, richard russel, william fulbright, robert byrd, etc, etc.
Strom Thurmond was the first southern politician to have african americans on his staff, while democrats remained lily white.