Did any groups following the US Civil War openly advocate a return to slavery?

by Adonnus

And how quickly did pro-slavery sentiment die out? Were there any political groups, factions or politicians who openly wanted its return?

Randomname64

I would not be able to answer how popular it was, but Buckner Payne published Ariel: or the Ethnological Origin of the Negro in 1867, which ends with a call to action, for slavery is a way to God's blessing and the rejection of slavery (and the racial amalgamation it brings) is a way to God's displeasure. So, at least two years after the Civil War, at least one preacher was calling for the restoration of slavery.

You might want to check out The Black Image in the White Mind, which goes into detail about the various responses to race and slavery both before and after the US Civil War.