McCain was never POTUS eligible.
He was a naturalized citizen—a citizen by statute.
The U.S. is not constrained by Natural Law or the Law of Nations but instead had and has always had its options about how to handle the question of whether and under what conditions the foreign born children of U.S. citizens are to be recognized as U.S. citizens.
By contrast, Congress since the adoption of the U.S. Constitution (which contains the uniquely exclusionary term natural born citizen) has never had any such discretion as to whether a child born here of a mother and a father, both U.S. citizens at the time, shall be recognized as a U.S. citizen. The U.S. Constitution, and the presence therein (and the original meaning) of the term in question, forces Congress’ hand, and denies it any such discretion. This is a good thing!
These debates shall go on and on until FR is no more, since neither side is going to be convinced by the other.