Sen. John McCain was on “Your World” this afternoon, where he slammed Sen. Rand Paul’s “fundamental lack of understanding” on the ISIS situation.

“Sen. Paul has obviously been doing some somersaults as these beheadings took place, and the American people's opinion has shifted rather dramatically,” he said. McCain said Paul has charged McCain with meeting with members of ISIS, which McCain called “patently false.”

McCain: ‘Has Rand Paul Ever Been to Syria?’

“I think it's kind of a desperation, kind of trying to find some footing here as he slides down a very steep slope of credibility.”

McCain also said he does not feel Paul would make a good commander-in-chief due to his position on national security.

Watch more above.