[DiogenesLamp]

the amendment only restricts the actions of the Congress of the United States. It does not prevent any state in the Union from taking action to end slavery in that state. Nor does it restrict the Congress of the United States from prohibiting slavery in any territory of the United States. So the amendment does not guarantee “permanent slavery” within the United States.

That's wishful thinking. I do not think you honestly believe that amendment would not have kept slavery going in the USA until it was no longer economically viable.

I try to be honest with myself, and I think you do too.

But why would the Northern states support such a measure?

[Bull Snipe]

“That’s wishful thinking.” No just a statement of fact. The Corwin Amendment does not prevent states from outlawing slavery if they so desire.

IMO When the first Southern States withdrew from the Union, member of Congress recognized why they chose to leave. 60 some odd resolutions were introduced into both houses of Congress to try and lure the Southern states back into the Union. The Corwin amendment was the one that the majority believed would work, if anything would. The overwhelming desire was to bring the Southern States back into the Union.
If slavery was allowed to exist in states where legal, so be it.