This message of Buchanan's hastened the inevitable separation of the Democratic party into its elements. The ablest Southern member of the Cabinet, Cobb, resigned. He was too strong an intellect to continue the policy of "nothing doing" now that the crisis had come. He was too devoted a Southerner to come out of political evasion except on one side. On the day Cobb resigned the South Carolina Representatives called on Buchanan and asked him not to make any change in the disposition of troops at Charleston, and particularly not to strengthen Sumter, a fortress on an island in the midst of the harbor, without at least giving notice to the state authorities. What was said in this interview was not put in writing but was remembered afterward in different ways with unfortunate consequences.

Every action of Buchanan in this fateful month continued the disintegration of his following. Just as Cobb had to choose between his reasonings as a Democratic party man and his feelings as a Southerner, so the aged Cass, his Secretary of State, and an old personal friend, now felt constrained to choose between his Democratic reasoning and his Northern sympathies, and resigned from the Cabinet on the 11th of December. Buchanan then turned instinctively to the strongest natures that remained among his close associates. It is a compliment to the innate force of Jeremiah S. Black, the Attorney-General, that Buchanan advanced him to the post of Secretary of State and allowed him to name as his successor in the Attorney-Generalship Edwin M. Stanton. Both were tried Democrats of the old style, "let-'em-alone" sort; and both had supported the President in his Kansas policy. But each, like every other member of his party, was being forced by circumstances to make his choice among the three inevitable courses, and each chose the Northern side. At once the question of the moment was whether the new Secretary of State and his powerful henchmen would hypnotize the President.