Ah yes, I remember Strom Thurmond, that great firebrand of the left, and his 1957 filibuster of the Civil Rights Act of 1957. Basically Lenin. /s

To be fair, US political culture (and capitalism in general) contain deep, deep contradictions so it's going to require a whole lot of glue and squinting to say that there is any coherence to any US political party...

The person you're responding to has it correct, though, that there was an important cultural shift around Johnson and Nixon and the Southern Strategy and all that... not that these cultural politics could ever touch the materialist facts of capital.