Final answer:
The demand for all new territories to be open to slavery during the 1848 election was part of the South's response to the Wilmot Proviso and Missouri Compromise, leading to increased sectional tensions and the Compromise of 1850 effort.
Step-by-step explanation:
During the 1848 election, the southern states championed the principle that all new territories should be open to slavery. This demand stemmed from the opposition to the Wilmot Proviso and the resentment toward the Missouri Compromise restrictions. Southerners argued for the right to take enslaved individuals into new territories, claiming it was about property rights and not wanting to be confined by northern mandates such as the Wilmot Proviso, which proposed barring slavery in territories acquired from Mexico. The question of slavery's expansion further complicated the national conversation on slavery, leading to the continuous sectionalism that would eventually contribute to the outbreak of the Civil War. The Compromise of 1850 attempted to address these issues by balancing the interests of free and slave states, yet it failed to resolve the deep-seated tensions between the North and the South on the expansion of slavery.