The Union had about 22 million people, and the Confederacy was about 5.5 million if you don’t count the slaves or about 9 million if you include them. So it’s not really half in that sense.

If you put all of the Union in the “approve” category and all of the Confederacy in the “disapprove” category (and not leave the slaves out of this) then Lincoln would have about an 80% approval rating, which is far higher than Trump can claim.