The Free Soil Party was organized for the 1848 US election to oppose further expansion of slavery into the western territories. Much of its support came from disaffected anti-slavery Democrats, including former President Martin Van Buren. The party was led by Salmon P. Chase and John Parker Hale and held its 1848 convention in Utica and Buffalo, New York. On June 22, Van Buren defeated Hale by a 154-129 delegate count to capture the Free Soil nomination, while Charles Francis Adams, the son and grandson of two other presidents, was chosen as the vice-presidential nominee.
Van Buren knew that the Free Soilers had not the slightest chance of winning, rather that his candidacy would split the Democratic vote and throw the election to the Whigs. Bitter and aging, Van Buren did not care despite the fact his life had been built upon the rock of party solidarity and party regularity. He loathed Lewis Cass and the principle of popular sovereignty with equal intensity.
1848 Free Soil & Liberty national Conventions Wikipedia
Despite their significant showing in the prior presidential election, certain events would conspire to remove the Liberty Party from political significance.
Initially, the nomination was to be decided in the fall of 1847 at a Convention in Buffalo, New York. There, Senator John P. Hale was nominated over Gerrit Smith, brother-in-law to the party's previous nominee James G. Birney. Leicester King, a former judge and state senator in Ohio, was nominated to be Hale's running mate. Anti-slavery Democrats and Whigs, disappointed with their respective nominees, would form a new movement in conjunction with members of the Liberty Party such as John Hale and Salmon Chase to form the Free Soil Party that summer. At this point, both Hale and King withdrew in favor of a Free Soil ticket led by former President Martin Van Buren, and the great majority of members of the Liberty Party followed. A small faction refused to support Van Buren for the presidency, however. They held another convention in June 1848 as the "National Liberty Party." Gerrit Smith was nominated almost unanimously with Charles Foote, a religious minister from Michigan, as his running-mate.