HW ? If slavery failed to expand, what effect would this have on the South's influence on national policy?

Answer 1

That would depend a lot on when it happened, but the long term result would have been to weaken the South's preferred policies--not only in terms of slavery but also in things like tariff, pro-British foreign policy, etc.

Answer 2

This is one of the largest causes of the Civil War. Slavery was failing and the South was losing what little influence it had on policy everyday. It was this unequal influence that led to the South attempting to leave and start their own country.