Nullification Crisis: Vice President of the United States John C. Calhoun pens the South Carolina Exposition and Protest, protesting the Tariff of 1828.

John Caldwell Calhoun (; March 18, 1782 March 31, 1850) was an American statesman and political theorist from South Carolina who held many important positions including being the seventh vice president of the United States from 1825 to 1832. He adamantly defended slavery and sought to protect the interests of the white South. He began his political career as a nationalist, modernizer, and proponent of a strong national government and protective tariffs. In the late 1820s, his views changed radically, and he became a leading proponent of states' rights, limited government, nullification, and opposition to high tariffs. He saw Northern acceptance of those policies as a condition of the South remaining in the Union. His beliefs and warnings heavily influenced the South's secession from the Union in 18601861.

Calhoun began his political career with election to the House of Representatives in 1810. As a prominent leader of the war hawk faction, Calhoun strongly supported the War of 1812. He served as Secretary of War under President James Monroe and, in that position, reorganized and modernized the War Department. Calhoun was a candidate for the presidency in the 1824 election. After failing to gain support, he agreed to be a candidate for vice president. The Electoral College elected Calhoun vice president by an overwhelming majority. He served under John Quincy Adams and continued under Andrew Jackson, who defeated Adams in the election of 1828, making Calhoun the most recent U.S. vice president to serve under two different presidents.

Calhoun had a difficult relationship with Jackson, primarily because of the Nullification Crisis and the Petticoat affair. In contrast with his previous nationalism, Calhoun vigorously supported South Carolina's right to nullify federal tariff legislation that he believed unfairly favored the North, which put him into conflict with unionists such as Jackson. In 1832, with only a few months remaining in his second term, Calhoun resigned as vice president and entered the Senate. He sought the Democratic Party nomination for the presidency in 1844 but lost to surprise nominee James K. Polk, who won the general election. Calhoun served as Secretary of State under President John Tyler from 1844 to 1845, and in that role supported the annexation of Texas as a means to extend the slave power and helped to settle the Oregon boundary dispute with Britain. Calhoun returned to the Senate, where he opposed the MexicanAmerican War, the Wilmot Proviso, and the Compromise of 1850 before he died in 1850. He often served as a virtual independent who variously aligned as needed, with Democrats and Whigs.

Later in life, Calhoun became known as the "cast-iron man" for his rigid defense of white Southern beliefs and practices. His concept of republicanism emphasized approval of slavery and minority states' rights as particularly embodied by the South. He owned dozens of slaves in Fort Hill, South Carolina. Calhoun asserted that slavery, rather than being a "necessary evil", was a "positive good" that benefited both slaves and owners. To protect minority rights against majority rule, he called for a concurrent majority by which the minority could block some proposals that it felt infringed on their liberties. To that end, Calhoun supported states' rights, and nullification through which states could declare null and void federal laws that they viewed as unconstitutional. He was one of the "Great Triumvirate" or the "Immortal Trio" of Congressional leaders, along with his colleagues Daniel Webster and Henry Clay.

The nullification crisis was a United States sectional political crisis in 1832–33, during the presidency of Andrew Jackson, which involved a confrontation between the state of South Carolina and the federal government. It ensued after South Carolina declared the federal Tariffs of 1828 and 1832 unconstitutional and therefore null and void within the sovereign boundaries of the state. However, courts at the state and federal level, including the U.S. Supreme Court, repeatedly have rejected the theory of nullification by states.The controversial and highly protective Tariff of 1828 was enacted into law during the presidency of John Quincy Adams. The tariff was strongly opposed in the South, since it was perceived to put an unfair tax burden on the Southern agrarian states that imported most manufactured goods. The tariff's opponents expected that Jackson's election as President would result in a significant reduction of it. When the Jackson administration failed to take any action to address their concerns, South Carolina's most radical faction began to advocate that the state declare the tariff null and void within the state. In Washington, an open split on the issue occurred between Jackson and Vice President John C. Calhoun, a native South Carolinian and the most effective proponent of the constitutional theory of state nullification; the legal theory that if a state believed a federal law unconstitutional, it could declare the law null and void in the state. This legal theory has been rejected at state and federal level.On July 1, 1832, before Calhoun resigned the vice presidency to run for the Senate, where he could more effectively defend nullification, Jackson signed into law the Tariff of 1832. This compromise tariff received the support of most Northerners and half the Southerners in Congress. But it did not satisfy South Carolina, and on November 24, 1832, a state convention adopted the Ordinance of Nullification, which declared that the Tariffs of 1828 and 1832 were unconstitutional and unenforceable in South Carolina after February 1, 1833. South Carolina initiated military preparations to resist anticipated federal enforcement, but on March 1, 1833, Congress passed both the Force Bill—authorizing the President to use military forces against South Carolina—and a new negotiated tariff, the Compromise Tariff of 1833, which was satisfactory to South Carolina. The South Carolina convention reconvened and repealed its Nullification Ordinance on March 15, 1833, but three days later, nullified the Force Bill as a symbolic gesture of principle.

The crisis was over, and both sides found reasons to claim victory. The tariff rates were reduced and stayed low to the satisfaction of the South, but the states' rights doctrine of nullification remained controversial. By the 1850s, the issues of the expansion of slavery into the western territories and the threat of the Slave Power became the central issues in the nation.