I understand that 2 divergent political economies was behind the divide causing the Civil War, namely the protectionist industrial north and the free trade export agricultural economy of the south. This came to a head when a candidate that was a free soiler in regards to the territories (Lincoln) won despite not even appearing on many southern ballots.
The proposed Corwin ammendment makes it clear that slavery was never threatened where it currently existed, so the conflict was over the restriction of the slave based political economy in regards to the future of federal government policy, the idea being that without the admission of new slave states the balance of power in congress would swing forever in the pro tariff party favor.
My question is why would new free states be assumed to support the protectionist tariffs? It seems that was the assumption but I don't fully understand what protectionist tariffs designed to improve the competitive viability of northeastern textile firms would be in the interest of western settlers, especially as it would likely raise the price of certain goods available to them. I understand why free farmers would be opposed to slavery, but since the future control of tariffs seems to be what really led to secession, why was it taken as a given that the new western free-soil states would also support the protectionist tariffs? What's in it for them?
A lil addendum here...or were there other issues perceived by the south in regards to the geographical restriction of slavery. Like idk...soil depletion or land prices skyrocketing/ slave values dropping or maybe fears around the concentration of slaves...I just see that there was made every concession possible to the southerners regarding the protection of the institution where it stood, so secession was deemed necessary simply because the system could no longer expand. What made that lack of expansion appear as an existential threat to southern slave holders?