Final answer:
The collapse of the Second Party System was catalyzed by sectional disputes over slavery and territorial expansion, leading to the decline of the Whig Party and the rise of new parties, most significantly the Republican Party, with a strong anti-slavery platform.
Step-by-step explanation:
The collapse of the Second Party System in the mid-19th century was caused by escalating tensions related to slavery and territorial expansion. The election of Franklin Pierce in 1852 temporarily held the nation together, with expectations that he would maintain the Fugitive Slave Law and support the interests of slavery. However, the ensuing efforts to spread slavery into new territories, such as the attempt to annex Cuba and the controversy over slavery in Kansas, heightened national division. As a result, the Whigs faced a steep decline and disintegrated as a national party post the 1852 election. Several new parties emerged in the wake of the Whig Party's downfall. Most notably, the Know-Nothing Party, also known as the American Party, and the Republican Party began to gain traction. The Republican Party quickly rose to prominence, particularly with its strong base in the Northern states, reflecting the increasing divide between North and South. The Republicans' opposition to the expansion of slavery in the territories resonated with many Northerners, which contributed to the disintegration of the Second Party System. The events leading to the collapse of the Second Party System signify how sectional disputes and the issuances of slavery set the stage for political reorganization and the rise of a new political ideology that sought to address these divisive issues, eventually leading to the American Civil War.