Answer:
The single-issue party that worked to stop the spread of slavery was the Free Soil Party.
Explanation:
The Free Soil Party was a political party that was active in the presidential elections of 1848 and 1852.
The political leadership of the party consisted of anti-slavery members of the Whig Party and the Democratic Party whose purpose was to oppose the spread of slavery in the territories of the West, arguing that free men on free territories constituted a morally and economically superior system to slavery. It opposed slavery in many federal states and tried to change the laws that in some states like Ohio discriminated blacks.
In the 1848 elections, former president Martin Van Buren was nominated. After the defeat in the 1852 elections, party members were mostly absorbed by the Republican Party in 1854.
