When thinking about the Civil War this is how I see it... When South Carolina seceeded from the Union --- it decided that being in a union or was staying under the protections of the U.S. Constitution was not important enough to its survival and future. There was no union of Southern States or Constitution or any guarantee there would be when South Carolina jumped ship. In fact when South Carolina seceeded the "union" was divided legally, economically, politically, culturally and geographically, so "preserving" it was a moot point-- it didn't exist. STOP!

Now....

So going back to the original question and paraphrasing it "which is more important - union or constitution" and thinking of ONLY those two words...

union- [A combination so formed, especially an alliance or confederation of people, parties, or political entities for mutual interest or benefit.]
constitution- [The system of fundamental laws and principles that prescribes the nature, functions, and limits of a government or another institution.]

I say a union is more important than a constitution because it gives strong protection to any group. A constitution may or may not apply to a group and only applies to organization.

But my answer could change if I had a better question with MORE contex.

Whew!

David