George M. Dallas
Dallas was important in the Senate, where he worked to support Polk and cast several tie-breaking votes. Dallas called for the annexation of all of the Oregon Territory and all of Mexico during the Mexican–American War, but accepted compromises that gave the United States parts of both areas. Though Dallas could not stop Polk from appointing Buchanan as Secretary of State, he helped convince Polk to appoint Robert J. Walker as Secretary of the Treasury. As vice president, Dallas tried to make himself a potential candidate for president in the 1848 election. However, his tie-breaking vote to lower a tariff destroyed much of his base in Pennsylvania, and his advocacy of popular sovereignty for slavery made more opposition against him.