Final answer:
The Free-Soil Party was formed in the mid-19th century by antislavery Whigs, Democrats, and Liberty Party members, with the key objective to oppose the expansion of slavery into new territories, challenging the pro-slavery stances of the dominant Whig and Democratic parties.
Step-by-step explanation:
The emergence of the Free-Soil Party in the mid-19th century marked a significant moment in American political history, deeply rooted in the contentious issue of slavery and its expansion into new territories. This new political entity attracted a diverse coalition, including disgruntled Whigs, antislavery Democrats, and members of the Liberty Party, unified by the philosophy encapsulated in the slogan, 'Free Soil, Free Speech, Free Labor, and Free Men.' The fundamental goal was to prevent the spread of slavery into newly acquired lands, reflecting a broader fear of a slave power conspiracy believed to be influencing national politics for the protection and expansion of slavery.
In resisting the nominations of pro-slavery candidates by both the Democrats and Whigs, the Free-Soil Party saw its inception in 1848. The Free-Soilers nominated Martin Van Buren for president, advocating for a platform that opposed the creation of new slave states and territories, seeking to appeal to a broad spectrum of voters concerned with the moral, economic, and political implications of slavery's expansion.