Which party dragged its heals?

In view of the recent U.S. Senate vote to apologize for slavery (a resolution long, long overdue, btw), the remarks of my far-Left senator, Tom Harkin, need to be held up to the light of historical evaluation.

Why did it take so long, anyway?

Hint: The political party responsible wasn't the one that was organized with the explicit purpose of fighting slavery.

It was the one responsible for Jim Crow... and the Civil War.