The main issue of the 1840s free soil party was that

The Free Soil Party was a short-lived political party in the United States active in the 1848 and 1852 presidential elections, and in some state elections. Founded in Buffalo, New York, it was a third party and a single-issue party that largely appealed to and drew its greatest strength from New York State. The party leadership consisted of former anti-slavery members of the Whig Party and the Democratic Party. Its main purpose was opposing the expansion of slavery into the western territories, arguing that free men on free soil comprised a morally and economically superior system to slavery. They opposed slavery in the new territories (agreeing with the Wilmot Proviso) and sometimes worked to remove existing laws that discriminated against freed African Americans in states such as Ohio.