Sen. John McCainJohn Sidney McCainGOP strategist donates to Alabama Democrat Meghan McCain knocks Bannon: 'Who the hell are you' to criticize Romney? Dems demand Tillerson end State hiring freeze, consult with Congress MORE (R-Ariz.) suggested Sunday that Sen. Rand PaulRandal (Rand) Howard PaulLexington mayor launches bid for Congress Trump-free Kennedy Center Honors avoids politics Meet the Iran hawk who could be Trump's next secretary of State MORE (R-Ky.) had little credibility in the fight against terror, saying that the Boston bombing had proved his views wrong.

McCain, in an interview on CNN's State of the Union, was asked to respond to Paul’s statements calling the National Security Agency’s phone tracking program an "all-out assault on the Constitution."

"Right. Just prior to the Boston bombing, he said the battlefield was no longer in America," McCain said. 

McCain's comment referenced an interview with Fox News where Paul criticized members of his party for saying that the fight against terror must be global in nature. 

"President Obama says this," Paul said in that interview. "Some members of my party say the battle has no geographic limitations and the laws of war apply. It's important to know that the law of war that they're talking about means no due process."

McCain also criticized Paul over Iran policy, saying “he's the only one that voted that Iran must not be just contained in pursuit of nuclear weapons. I disagree."

Paul has been a sharp critic of the NSA’s surveillance of phone calls and the internet. But McCain defended those programs Sunday as critical to U.S. security.

McCain and Paul have repeatedly clashed over national security. 

After Paul held a 13-hour filibuster on John Brennan's nomination to run the CIA over the nation’s drone policy, McCain called Paul and Sen. Ted CruzRafael (Ted) Edward CruzDebbie Wasserman Schultz marks 10 years as breast cancer survivor Foreign agent registration is no magical shield against Russian propaganda Let Trump be Trump and he'll sail through 2020 MORE (R-Texas), who joined the filibuster, "wacko birds."

Paul last week mocked McCain’s secret trip to Syria to meet with opposition forces after photos appeared showing McCain with two men accused of kidnapping Shiite civilians.

“We had a senator over there who had his picture taken with some kidnappers, so I don’t know how good a job we’re doing vetting those who are going to get the arms,” Paul said in a speech criticizing McCain’s call to arm pro-Western Syrian rebel groups.