That's why it's not an argument actual historians and political scientists make, but rather one partisan hacks use as a straw man.
I mean, this is the whole reason why Strom Thurmond's switch was such a huge deal at the time. It was historic because it was rare!
But they always fell apart on the issue of southern Democrats' seniority.
Without the same guarantees that Thurmond had been given, no senior southern Dems would jump.
But they encouraged the next generation of white conservatives in the South start their careers in the GOP.
They were all former Democrats who jumped to the GOP over the Civil Rights Act, who then voted against the Voting Rights Act and opposed civil rights activists.
Colmer chose Lott to succeed him in 1972, but had him run as a Republican.
That's not the only way realignment took place.
In Virginia, Dem. Gov. Mills Godwin, an outspoken leader of segregationist resistance, switched parties and won re-election as a Republican in 1973.
In 1968, for instance, five of the top officeholders in Georgia switched from the Democrats to the Republicans:
Again, the idea that everything changed in a flash in 1964 *is* silly. That's why it's only used by hacks as a cheap straw man.