Though he had previously helped maintain a balance between the Barnburners and Hunkers , the two factions of the New York Democratic Party , Van Buren moved closer to the Barnburners after the 1844 Democratic National Convention . The split in the state party worsened during the Polk 's presidency , as his administration lavished patronage on the Hunkers . In his retirement , Van Buren also grew increasingly opposed to slavery . As the Mexican – American War brought the debate over slavery in the territories to the forefront of American politics , Van Buren published an anti-slavery manifesto . In it , he refuted the notion that Congress did not have the power to regulate slavery in the territories , and argued the Founding Fathers had favored the eventual abolition of slavery . The document , which became known as the " Barnburner Manifesto , " was edited at Van Buren 's request by John Van Buren and Samuel Tilden , both of whom were leaders of the Barnburner faction . After the publication of the Barnburner Manifesto , many Barnburners urged the former president to seek his old office in the 1848 presidential election . The 1848 Democratic National Convention seated competing Barnburner and Hunker delegations from New York , but the Barnburners walked out of the convention when Lewis Cass , who opposed congressional regulation of slavery in the territories , was nominated on the fourth ballot
1848 Democratic National Convention
1848 Democratic National Convention
Martin Van Buren