That's what this is about. He said a few days ago that he would have beaten Lincoln by 35 points (technically he said someone told him that, which is a lie). Then he says that the Civil War could have been negotiated (ie, he could have "negotiated" it), so Lincoln wasn't all that great. He was the best president!
It's total nonsense, of course (and he won't try to explain how those negotiations could have happened), but he is not trying to make any real sense.