In their view, secession would preserve slavery as it existed at the time they seceded. A rational thought, if they felt their economic underpinnings were threatened by the ideas of a Republican majority Congress and a Republican President.
It would not have changed. Any rational person can see that slavery would have continued in the Union unchanged as it had been for "four score and seven years".
You are asserting that the illusion of change was the cause of the war. Of course they didn't expect a war, so it's hard to see how you can assert that even the illusion that slavery was threatened could have led to a war.
A rational thought, if they felt their economic underpinnings were threatened by the ideas of a Republican majority Congress and a Republican President.
It's hard to see how anyone could rationally have believed that. Firstly it was constitutionally impossible, and secondly both Lincoln and the Congress had offered them additional constitutional protections, which somehow didn't sway them at all.
There was no real potential of any changes to their system either in or out of the Union. This is why I point out that the claim the war was about slavery doesn't make any sense, and I have since come to regard it as just propaganda to justify what was done to them.