In alliance with pro-expansion northern Democratic colleagues , they secured the nomination of James K. Polk , who ran on a pro-Texas Manifest Destiny platform .
Pro-Texas - annexation southern Democratic delegates denied their anti-annexation leader Martin Van Buren the nomination at their party 's convention in May 1844 .
In alliance with pro-expansion northern Democratic colleagues , delegates secured the nomination of James K. Polk , who ran on a pro-Texas Manifest Destiny platform .
Pro-Texas - annexation southern Democratic delegates denied their anti-annexation leader Martin Van Buren the nomination at their party 's convention in May 1844 .