In the months leading up to the 1844 Democratic National Convention , former President Martin Van Buren was widely seen as the front-runner for the Democratic presidential nomination . Polk , who desired to be the party 's vice-presidential nominee in the 1844 election , engaged in a delicate and subtle campaign to become Van Buren 's running mate . The potential annexation of the Republic of Texas by President John Tyler upended the presidential race ; while Van Buren and the Whig frontrunner , Henry Clay , opposed the annexation and a potential war with Mexico over the disputed territory , Polk and former President Andrew Jackson strongly supported the territorial acquisition . Disappointed by Van Buren 's position , Jackson threw his support behind Polk for the party 's 1844 nomination
1844 Democratic National Convention
1844 Democratic National Convention
Presidency of James K. Polk