Why did the two political parties trade sides after the Civil Rights era?

Moderator Warning

Once again, political jabs are not permitted in General Questions. This is an official warning. Do not do this again.

This goes for everyone.

Colibri
General Questions Moderator

Reread my first post. Both parties had a liberal wing. Both parties supported the Civil Rights Act. As a total entity, the Democrats became more identified with civil rights starting in the 1930s because of northern Democrats and Eleanor Roosevelt active advocacy but both parties had a faction in support until after Nixon. Who is saying otherwise?