The economy of the South was dependent on staple agriculture mostly of the agribusiness plantation form. The Republicans who were just Hamilton's descendents and mostly northern Whigs knew their crony capitalist model which was their true core reason to exist would never attract enough votes to defeat the Democrats. So the GOP spent a decade screaming about slavery to troll for enough voters in the north to give them the edge. Lincoln and Seward could care the less about slavery as long as it stayed in the South and Southerners paid most of the cost of the tariffs on manufactured items. With that dough they could pay off the speculators and bankers and railway interests that were the powerbase of the party.
Unfortunately people in the South believed windbags like Seward and after the events surrounding John Brown believed they were facing an existential threat from the north of the most basic kind. Lincoln never figured that out as did many northerners and were shocked and then outraged when they realized the South was serious about forming its own country and breaking the rice bowls of many northern capitalists.
This I think is the real basis for the secession crisis and the war that followed. It is much to grubby to justify the hideous destruction of the war and the hundreds of thousands of casualties so the ‘glory, glory, hallelujah, version became the default.
It was known long before the windbags showed up...and it wasn't a belief, it was a fact.
The 'personal liberty laws' were nothing more than Nullification laws, and showed exactly which way the winds had begun blowing.
If the South were to violate any part of the Constitution intentionally and systematically, and persist in so doing, year after year, and no remedy could be had, would the North be any longer bound by the rest of it? And if the North were deliberately, habitually, and of fixed purpose to disregard one part of it, would the South be bound any longer to observe its other obligations? I have not hesitated to say, and I repeat, that if the Northern States refuse, willfully and deliberately, to carry into effect that part of the Constitution which respects the restoration of fugitive slaves, and Congress provide no remedy, the South would no longer be bound to observe the compact. A bargain cannot be broken on one side and still bind the other side.
Life of Daniel Webster, Speech at Capon Springs / 1851 / Vol 1 / page 518