I believe that you are right on this point. I have not specifically researched this topic, but I have read many original ante bellum documents, especially wills and probate documents. I have a letter, written by a North Carolina ancestor in 1784 to his cousins in Ireland. He lamented the survival of slavery into the New Republic and predicted its end in due course. He also predicted that if the country could not craft a solution, a civil war would ensue. He was a slave holder and Revolutionary War officer. I have read many other contemporary accounts by the political and social elites debating how to end the institution.
But, by the 1850's, this talk had disappeared. I think in part this was just a hardened political stance in response to external attacks by the abolitionist movements in the North and in England. They took the stance that abolition was easy in England and the North where Industrialization provided the only economic engine required. The South, they contended, could not survive economically without slaves. It was a rationalization in my opinion, but it was one that was wildly held.
The other factor was the cotton gin. Before its invention, slave based plantation agriculture was a low country activity. In the Piedmont and Western states, the Scots Irish and German settlers held few slaves and operated small subsistence family farms. The cotton gin changed this. The upland farmers, with slave labor, could grow abundant crops of cotton and many of these poor Southerners became very wealthy men. Prosperity changes attitudes, and many who held moral objections to slavery adjusted their stance. Of course, when the vote to secede came, many of those upland dwellers voted against it, but they had become the minority.
BTW, all of my ancestors were Southerners, including some well known slave holders like Thomas Jefferson. With the exception of a very small group who left Tennessee and went to Illinois in protest of slavery, all of the rest supported slavery either explicitly, or implicitly through their service to the Confederate cause.
The southern belief that they were utterly dependent economically on slavery was absolutely correct.
For more than 50 years most southern capital had been poured into investments in slaves, to the point where the value of the slaves (human capital in the literal sense) was considerably greater than the value of all the land and buildings in the South. Emancipation would have, and indeed did, make all that wealth just disappear, the primary reason for southern poverty after the war, not carpetbagger oppression.
Think of the turmoil here when we have had a disappearance of perhaps 20% to 25% of real estate values. Then extrapolate that to 100%. No wonder they were scared to death.
I haven’t seen much discussion of the topic, but I suspect slavery in 1860 was nearing the end of a classic bubble. There is no way the amount of money a slave could bring in could justify the huge prices being paid for a slave.
People invested in slaves because they expected the price to go up. It was believed that restriction of slavery to its present bounds would bring the price down, bursting the bubble.
In actual fact, of course, the slave price bubble was doomed, anyway. The high price of cotton on which it was based was encouraging cotton growing in other areas like Egypt and India, and thus an expansion of supply, which would have eventually brought down the price. The War just accelerated this process.
Southerners were under the delusion they could keep the bubble expanding indefinitely by building a great slave empire in Latin America and the Caribbean. In actual fact the Royal Navy would never have allowed them to do so. Not to mention the rump of the USA.
The evil of the South’s position came not from recognition of their total dependence on the institution, but rather from their determination to proclaim an evil institution to be a positive good. Along with Lincoln, I have no idea how the evil could be gotten rid of. But I know calling evil good is always wrong.