I could see him being one of the Democrats, like Horatio Seymour, who goes "The Civil war is necessary, but Lincoln has screwed us all!" If he does take such an attitude he could help strengthen the bourbons a bit by showing Pre-war Democrats that "This is the right way for the party." Although the fact he ran on the ND ticket could in some way weaken the southern grasp on the south. Overall, he'd probably be irrelevant by the 1880s, but he could be a major voice in the 1860s-70s