Regarding a "Republic". See my tagline.
The fact is, the reason the South Seceded is they refused to abide by the rules of the Republic. They saw the writing on the wall. With every free state added the congress would become more and more against slavery and before long the South would lose its "peculiar institution". So, they tried to leave in order to preserve it.
I think history proves that it's the other way around. Numerous northern states refused to honour certain parts of their agreement, just as Congress and Lincoln refused to abide by a certain Supreme Court decision. Thus the Confederate states were faced with the prospect of remaining in a union with states that would not abide by their agreement, they exercised their constitutional powers, convened conventions of the people of the state, and voted to leave and resume their delegated powers.
Once the states departed, Congress did not declare war on them. They did not invade the states to drag them back into the union by force. Diplomatically, the Confederate states attempted to resolve all issues peacfully, but their efforts were repeatedly rebuffed by Lincoln. The Confederate Congress enacted a tariff of about 10%, a HUGE decrease from the Morrill tariff rates of well over 40%. Then, and only then, did the North understand that the South's $300,000,000+ exports (foreign and previously domestic) would raise huge sums for the Confederacy, while the North would no longer be guaranteed protection via tariff, and lose millions in revenue.
Which explains Lincoln's stated use of force to collect the tariff unless the Confederate states rejoined the union. A tryant, by any other name, is still a tryant.
... and before long the South would lose its "peculiar institution". So, they tried to leave in order to preserve it.
Nonsense, if slavery was all they desired, all they had to do was remain IN the union and accept the North's - and Lincoln's - offer of Constitutionally permanent slavery. If slavery was what the Confederate states desired - their was no need to leave.