They literally fought for slavery. Lincoln was the first Republican because the country needed a third party to actually represent the voters and defeat the slavery party. And then he needed another third party because they bought enough influence in the newly successful Republican party who wouldn't support him for his re-election. And he still won - Lincoln was both of the last two third party Presidents to be elected, after him they slammed that door shut to try and stop candidates from interfering with what they have always done. Meanwhile they went to war over keeping slaves because calling him "nazi" constantly wasn't their style yet. Its still their thing, their last Presidential candidate made a career of keeping slaves locked up even after her own state insisted they should be released.