Look at his face.  It's obviously one of those masks that the characters peeled off their faces at the end of Mission Impossible episodes.  Who knows who's in there, and what they've done with the real McCain?

Why can't he reveal his medical records, hmmmm?  That's right: different blood-type.

This is why he can't keep his stories straight - the new McCain honestly doesn't know what the old McCain was up to.

The new McCain:  even stupider than the old McCain.