He was too good a politician to yield, even if there had been no other reason to stand firm, but continued to defend the only doctrine on which there was the slightest chance of beating the Republicans in the approaching election. One method he took to defend it was novel, but he has had many imitators among public men of a later day. He wrote out his argument for "Harper's," the most popular magazine of the day. The article is not nearly so good reading as his speeches, but it was widely read. Judge Jeremiah Black, the Attorney-General of Buchanan's cabinet, made a reply to it, and Douglas rejoined; but little of value was added to the discussions in Congress and on the stump. The Southerners, however, would not take warning. As they saw their long ascendency in the government coming to an end, their demands rose higher. Some of them actually began to agitate for a revival of the African slave trade; and this also Douglas had to oppose. His following in the Senate was now reduced to two or three, and one of these, Broderick, of California, a brave and steadfast man, was first defeated by the Southern interest, and then slain in a duel. John Brown's invasion of Virginia somewhat offset the aggressions of the South; but that, too, might have gone for a warning. The elections in the autumn of 1859 were enough to show that the North was no longer disposed to forbearance with slavery. Douglas went as far as any man in reason could go in denouncing John Brown and those who were thought to have set him on; and he supported a new plan for getting Cuba. But Davis, on the very eve of the Democratic convention at Charleston, was pressing upon the Senate a series of resolutions setting forth the extreme demand of the South concerning the Territories. He was as bitter toward Douglas as he was toward the Republicans. At Charleston, Yancey took the same tone with the convention.