Two reasons northern politicians feared the expansion of slavery in the West was

To many nineteenth century Americans, the expansion of slavery into Western territories caused a great deal of controversy. Since the drafting of the Constitution in 1787, the North and the South had grown further apart in terms of economy, ideology, and society. The North, especially, was afraid that the South would force its “peculiar institution” upon the entire Union.  These fears were realized when the expansion of slavery into western territories entered Congressional debates. The federal government, hoping to prevent a civil war, temporarily resolved the issue with compromises. As the compromises appeared to become more one-sided, however, sectional divides between the North and South became more pronounced.

discrimination! they faced a lot of racism