Over time, the Democratic party become less conservative, and the Republican party more conservative.
Conservative Democrats promoted slavey and even wrote Jim Crow laws and started the KKK
In 1964 when the Civil Rights Act was signed, Conservative Dixiecrat Democrats switched to the Republican party to spite Lyndon Johnson. Richard Nixon also recruited these Conservative Democrats under his "Southern Strategy" effort.
Conservatism is the only common thread to pre-1940 racist and bigoted Democrats and post-1964 racist and bigoted Republicans.
