The question of Slavery became too polarizing in the election of 1860, with extremists on either side of the Slave issue leading the charge.  The Republicans ran a Free State campaign, the Democrats split into two parties over degrees of supporting Slavery, and a forth party shunning both sides joined the chaos.  Abraham Lincoln gained only 40% of the national vote, but won every Northern State.  No one voted for him in most of the Southern States.  It was the end.