So, I'm considering a scenario for the alt-Civil War. First, with the changes to the constitution not requiring an actual majority to win the Presidency, just the most electoral votes, we will see a southern Republican win the Presidency with the Federalists and Democrats splitting the abolitionist message. This in itself doesn't set things off, but the assassination of this president will. His successor takes a hardline against the abolitionists in the wake of the assassination. Furthermore, the successor gets reelected thanks to the same vote split, and it things hit the fan after that.
But, instead of the South seceding, it will be Federalist-dominated New England that tries to break away, and other Northern states will end up following in response to Union actions against the rebels.
Thoughts?