Finding it impossible under the two-thirds rule to nominate their candidate, the followers of Van Buren brought forward Polk, who was popular in the South, in order to defeat Lewis Cass and James Buchanan.
Part of Polk county, and forming near its entrance into the Gulf of Mexico the boundary between Levy and Citrus counties, and four rivers, the Escambia, the Choctawatchee, the Apalachicola, and the Suwanee, having their sources in other states and traversing the north-western part of Florida.
The centre of the quarries is Dunnellon in Marion county, and pebble phosphate is found in Hillsboro, Polk, De Soto, Osceola, Citrus and Hernando counties.
He was vicepresident of the United States from 1845 to 1849, but the appointment of Buchanan as secretary of state at once shut him off from all hope of party patronage or influence in the Polk administration, and he came to be looked upon as the leader of that body of conservative Democrats of the North, who, while they themselves chafed at the domination of southern leaders, were disposed to disparage all anti-slavery agitation.
In 1844 he was chosen as a presidential elector on the Polk and Dallas ticket; in February 1845 he married Miss Varina Howell (1826-1906) of Mississippi (a granddaughter of Governor Richard Howell of New Jersey), and in the same year became a Democratic representative in Congress.