We all know what happened in April 1865...
(That would have been an odd-looking pair. Had BB accepted, he and Lincoln would have had a 13" difference in height between them. Lincoln was 6' 4", and Butler claimed to be 5' 3" , so if he was like most men , he was probably even shorter. Even in those less looks-conscious years, they would have looked a bit strange stumping together.)
BB never quite recovered from that one, either. He ran unsuccessfully for the presidency as a third party candidate IIRC, and I believe he did get elected as a senator, but I'm not 100% sure of that.
President "Spoons" Butler?