Bordeaux AOC Declassification Question

Hi - I'm caught up on the AOC level of Haut-Medoc. Since it is both the region that contains Pauillac, Margaux, etc, and its own AOC area, I'm not sure how it fits into the hierarchy.

So if you were had a Pauillac wine and needed to declassify it for any reason, would the next level down be Haut-Medoc or Medoc?

Related, if you blended grapes from Margaux and Haut-Medoc, how would that wine be labeled?