Recolonization of slaves and complete abolition of slavery.
Three groups emerged in the 1830's-1840's each with a differing view of how to end or contain slavery. The most conservative approach was the recolonization approach. The American Colonization Society created the colony of Liberia with the intent of freeing slaves and sending them back to Africa. The most liberal approach came from the Liberty Party who advocated for the complete end of slavery based on moral grounds. The Liberty Party wanted slavery to end immediately with blacks receiving citizenship rights.
The moderate approach to slavery that emerged at the time didn't directly end slavery but hoped to contain the institution. Free-soilers emerge after the Mexican-American War and believed that the new land gained should be free from slavery. By containing slavery to the South, the system would eventually snuff itself out without extra land available to expand the system.