Cox was re-elected in 1858 by a slightly larger majority. He remained an opponent of the Buchanan administration and an ally of Senator Douglas amid growing sectional and political divide in Congress. In 1860, despite growing divisions and the election of Abraham Lincoln, Cox expanded his majority again, in a rematch with Galloway. As Southern states began to secede in the winter of 1860–61, Cox issued a plea for unity and caution. When Senator Douglas died in 1861, Cox delivered a eulogy to him in the House.