Lincoln wanted the war over with. And so did the American people on both sides. When Grant was leaving for Appomattox Lincoln said to him “Let them up easy’’. It was obvious he didn’t want further resentment and rebellion if he tried him for treason.
And to make certain it happened even after his death, Lincoln in 1864 selected East Tennessee Democrat Senator Andrew Johnson to replace former Republican Maine Senator Hannibal Hamlin as his Vice Presidential running mate.