I agree with you. But to get Mac elected Atlanta will have to go differnetly so the south's fate isnt sealed so much. So many people seem to believe that Mac was for peace when he wasnt. This timeline shows that if the copperheads who getr him elected are fighting him in his cabinet and in congress that he will make a peace, but a peace that will ruin the South. No reperations, the north refuses to return slaves, the south is forbidden to expand territorily and is forbidden to allow foriegn troops to be staion on its soil or to sell its lands to foreign nations except US. As well as arming freed slaves in the south. All this bring the south to its knees as it economy collapses and the already exhausted southerners are forced to put down black revolts. This leads to the gradual reannexation of each of the confederate states, one by one, ending probably in the early 1900's.
I dont think this is a likely TL but I think it is alot more probable than all other TLs revolving around the elections of 1864 that some *ahem* pro-confederates on the board post.