Recently I came across this quote from John C. Calhoun:
I consider the tariff act as the occasion, rather than the real cause of the present unhappy state of things. The truth can no longer be disguised, that the peculiar domestick [sic] institution of the Southern States and the consequent direction which that and her soil have given to her industry, has placed them in regard to taxation and appropriations in opposite relation to the majority of the Union, against the danger of which, if there be no protective power in the reserved rights of the states they must in the end be forced to rebel, or, submit to have their paramount interests sacrificed, their domestic institutions subordinated by Colonization and other schemes, and themselves and children reduced to wretchedness.
I always assumed that while the civil war was mainly about slavery, legitimate grievances related to tariffs and what have you did exist and also played a part, but this quote seems to suggest that even the tariff issue was really about slavery at it's core. Are there any other contemporary sources to that effect? Or modern histories that give a good overview of the role slavery played in the nullification crisis?
The consensus is that Calhoun was basically right. He ought to know, considering he's deeply enmeshed in the whole thing. That's the position taken by both the modern histories of the subject, Freehling's Prelude to the Civil War and Ellis' The Union at Risk, though Ellis tapdances around it a bit because he really wants to talk about state's rights constitutionalism as if it has no connection to practical outcomes.
There are legitimate economic difficulties in South Carolina at the time and they were attributed to the tariff, but a significant contingent of nullifiers (lowcountry long staple cotton and rice guys) were not really feeling the pinch and the SC economy was on a bit of a rebound when nullification came. Period sources are generally clear that the tariff is wrong because it's a danger to slavery. By reducing the profitability of the state's agricultural products, which is dubious but some of them believed it, tariffs inherently reduced the profitability and thus price of slaves. With a lot of cash invested in people, a significant dip in prices might lead to panic selling, at which point they believed SC would enter into a death spiral toward emancipation, poverty, and probably race war. All the talk about the constitutionality or not of tariffs, theories of state's rights and nullification, arises from that.