William G. Andrews, "Vallandigham, Clement Laird," American National Biography Online, February 2000, http://www.anb.org/articles/04/04-01009.html.
Though he served only two terms in Congress, his evident political talents and ambition attracted national attention early. He was a delegate to four successive Democratic National Conventions and in 1860 was secretary of the Democratic National Committee and chair of its campaign committee. He frequently had important influence on the party's campaign platforms. During the Civil War, he was the most prominent leader of the "Peace Democrats," who were disparagingly nicknamed "Copperheads." That leadership made him the center of great controversy. His criticism of Lincoln and his administration was relentless and sometimes intemperate. Vallandigham was a fiery orator whose arguments often found very receptive audiences during the early years of the war when the Union army was suffering defeat after defeat and the casualty lists seemed endless.