How many of his fellow POWs have endorsed him?
You can start by googling the names of Col. Bud Day - the most decorated living veteran in the U.S. - who was a POW with McCain and vouches for him completely. He even has campaigned with him.
You can also add the name of Orson Swindle - who was a POW with McCain.
Sam Johnson, a member of Congress from Texas and a POW in Vietnam, has endorsed him. That’s just for starters.