Van Buren 's opposition to immediate annexation cost him the support of many pro-slavery Democrats . In the weeks before the 1844 Democratic National Convention , Van Buren 's supporters anticipated that he would win a majority of the delegates on the first presidential ballot , but would not be able to win the support of the required two-thirds of delegates . Van Buren 's supporters attempted to prevent the adoption of the two-thirds rule , but several Northern delegates joined with Southern delegates in implementing the two-thirds rule for the 1844 convention . Van Buren won 146 of the 266 votes on the first presidential ballot , with only 12 of his votes coming from Southern states . Senator Lewis Cass won much of the remaining vote , and he gradually picked up support on subsequent ballots until the convention adjourned for the day . When the convention reconvened and held another ballot , James K. Polk , who shared many of Van Buren 's views but favored immediate annexation , won 44 votes . On the ninth and final ballot of the convention , Van Buren 's supporters withdrew the former president 's name from consideration , and Polk won the Democratic presidential nomination . Though angered at the way in which his opponents had denied him in the Democratic nomination , Van Buren endorsed Polk in the interest of party unity . He also convinced Silas Wright to run for Governor of New York so that the popular Wright could help boost Polk in the state . Wright narrowly defeated Whig nominee Millard Fillmore in the 1844 gubernatorial election , and Wright 's victory in the state helped Polk narrowly defeat Henry Clay in the 1844 presidential election
1844 Democratic National Convention
1844 Democratic National Convention
Martin Van Buren