In 1848 he was again nominated, first by the "Barnburner" faction of the Democrats, then by the Free Soilers, with whom the "Barnburners" coalesced, but no electoral vote was won by the party.
After the defeat of Governor Silas Wright in 1846, however, the Democratic party split into two hostile factions known as the " Hunkers," or conservatives, and the " Barnburners," or radicals.
The split broke up the rule of the "regency," Marcy accepting the " Hunker " support and a seat in Polk's cabinet, while Wright, Butler and Van Buren joined the " Barnburners," a step preliminary to Van Buren's acceptance of the " Free Soil " nomination for president in the campaign of 1848.
It was a combination of the political abolitionists - many of whom had formerly been identified with the more radical Liberty party - the anti-slavery Whigs, and the faction of the Democratic party in the state of New York, called "Barnburners," who favoured the prohibition of slavery, in accordance with the "Wilmot Proviso" (see Wilmot, David), in the territory acquired from Mexico.
Between 1848 and 185 2 the "Barnburners" and the "Hunkers," their opponents, became partially reunited, the former returning to the Democratic ranks, and thus greatly weakening the Free Soilers.
Realizing in time that a third party movement could not succeed, he took the lead during the campaign of 1848 in combining the Liberty party with the Barnburners or Van Buren Democrats of New York to form the Free-Soilers.
In 1848 he received the Demo ratic nomination for the presidency, but owing to the defection of the so-called " Barnburners (see Free-Soil Party) he did not receive the united support of his party, and was defeated by the Whig candidate, Zachary Taylor.