The convention included three former vice presidents who sought the presidential nomination, John C. Calhoun, Van Buren and Richard Mentor Johnson.

Though his opposition to the annexation of Texas cost him support with expansionists and Southerners, former President Martin Van Buren entered the convention with the backing of a majority of the delegates.

After Senator Silas Wright of New York declined the vice presidential nomination, the convention selected Dallas as Polk's running mate.

[1] His principal opponent was Lewis Cass of Michigan, who had served as United States Secretary of War under President Andrew Jackson.

Middle and Deep South pro-annexationists opposed Van Buren 75 to 3, depriving northern anti-annexationists the 31 votes needed for victory.

[8] On the eighth ballot, the historian George Bancroft, a delegate from Massachusetts, proposed former Speaker of the House of Representatives James K. Polk as a compromise candidate.

[8] Although a slaveholder himself, Polk never enunciated a slavery expansionist position with respect to Texas annexation, as had John C. Calhoun and the southern extremists.

[13][14] Southern Democrats benefited from the Tyler-Calhoun machinations in eliminating Martin Van Buren as a presidential candidate, and clearing the way for the pro-annexation nationalist Polk.

Van Buren complied with his party's decision to unite under a pro-annexation candidate, and worked to win New York state for Polk.

[20] As a national imperialist, he exhibited an unwavering support for Manifest Destiny, perceived as a non-sectional devotion to expansionism, whether slave-soil Texas or free-soil Oregon Territory.

Polk's political reputation was expected to diffuse northern Democratic resentment towards the Slavepower, while delivering Texas to the Deep South.