His family moved (1806) to the Duck River valley in Tennessee and there, after graduating from the Univ. of North Carolina (1818) and studying law under Felix Grundy, he began (1820) to practice law in Columbia. Polk served in the state legislature (1823–25) and in the U.S. House of Representatives (1825–39), where he was speaker for the years 1835–39. He was a leading Jacksonian Democrat. In 1839 he was elected governor of Tennessee, but he was defeated for reelection by the Whig candidate in 1841 and 1843.
Polk had vice presidential ambitions, but Andrew Jackson, convinced that Martin Van Buren had committed political suicide by announcing his opposition to the annexation of Texas, urged Polk to consider the presidency. With the Van Buren and Lewis Cass factions deadlocked at the Democratic convention at Baltimore in 1844, George Bancroft advanced Polk as a candidate behind whom both sections could unite, and the "dark horse" won the nomination. Polk campaigned on an expansionist platform and narrowly defeated Henry Clay by carrying New York state, where the presidential candidacy of James G. Birney of the Liberty party cut into Clay's vote.
The Columbia Electronic Encyclopedia, 6th ed. Copyright © 2012, Columbia University Press. All rights reserved.