A Congressman (1811-17) and acting chairman of the House Committee on Foreign Affairs, Calhoun was one of the leading "war hawks," who whipped up enthusiasm for the War of 1812. He remained a nationalist for some time after the war, speaking for a strong army and navy, for encouragement of manufacturing, for internal improvements, and for a national bank; many of these causes he later opposed. Calhoun was an efficient Secretary of War (1817-25) under President Monroe.

Calhoun first served as Vice President (1825-29) under John Quincy Adams. Throughout Adams's administration he opposed the President and aligned himself with the supporters of Andrew Jackson. An able constitutional lawyer, he made an imposing figure skillfully presiding over the Senate. When the Jacksonians finally triumphed in 1828, Calhoun was again elected Vice President.

It was widely assumed that he would succeed Jackson in office, but relations between the two men soon cooled. Calhoun, prodded by his wife and his supporters, offended the President in the Eaton affair (see O'Neill, Margaret). Jackson finally became furious when he discovered that years before Calhoun had privately denounced Jackson's conduct in Florida while publicly giving the impression that he had supported the general. Primarily, however, Jackson and Calhoun had come to disagree on the nature of the Union.

As the preeminent spokesman for the South, Calhoun tried to reconcile the preservation of the Union with the fact that under the Union the South's dominant agricultural economy was being neglected and even injured for the benefit of the ever-increasing commercial and industrial power of the North. When a still higher tariff replaced (1832) the Tariff of Abominations of 1828, he maintained that the Constitution, rightly interpreted, gave a state the power to nullify federal legislation inimical to its interests. He returned to South Carolina, had a state convention called, and directed the passage of the famous ordinance of nullification.

In Dec., 1832, Calhoun quit the vice presidency after being elected to the Senate, where he eloquently defended his states' rights principles in dramatic debates with Daniel Webster. The firmness of Andrew Jackson and the compromise tariff proposed by Henry Clay resolved the nullification crisis in 1833, but the larger issue of states' rights persisted, leading ultimately to secession and the Civil War.

Martin Van Buren, Calhoun's bitter political enemy, held the vice presidency in Jackson's second term and went on to succeed Jackson in the office Calhoun had coveted for many years. As the abolitionists grew stronger in the North, Calhoun became an outspoken apologist for slavery and made every effort to maintain the delicate balance between North and South in the Senate by opposing the prohibition of slavery in newly admitted states. Thus, while serving briefly (1844-45) as Secretary of State under John Tyler, he completed negotiations for the admission of Texas as a slave state, but later tried to avert war with Mexico.

Again (1845-50) in the Senate, he advocated compromise in the Oregon boundary dispute but opposed the admission of California as a free state in the debates over the Compromise of 1850. In rejecting the Wilmot Proviso, Calhoun set forth the theory that all territories were held in common by the states and that the federal government merely served as a trustee of the lands.

His Disquisition on Government and Discourse on the Constitution and Government of the United States, both published posthumously, crystallized his political philosophy. The Constitution, he stated, established a government of concurrent majorities composed of two elements—the state governments and the federal government. Hence the states enjoy the power of veto, or nullification, and the right of secession results necessarily from the origin of the Union as a compact among the sovereign parties. His theories attempted to formulate democracy in terms of protection for a minority, specifically, the South, and they were later embodied in the Confederate constitution. Because his ideas are associated with an institution—slavery—offensive to the idealism of most Americans, Calhoun has not been a popular figure in U.S. history.