system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How did the Republican and Democratic party basically switch rolls between the Civil War and now?
gpt
In 1948, the Democratic Party, at their convention, voted to add Civil Rights to their party platform.  When this happened, the southern racist Democrats, led by Strom Thurmond, left the party and started the Dixiecrat Party.  They were a viable third party for a while.

Then, in the 60s, President Johnson (a Democrat) signed the Voting and Civil Rights Acts.  When Nixon ran in '68, he used this to lure the Dixiecrats into the Republican Party using what became known as the "Southern Strategy."  And that's pretty much how it's been since.