Sen. Rand Paul (R-Kentucky) is becoming New Jersey Gov. Chris Christie's (R) campaign-trail punching bag.

In an interview Monday on MSNBC's "Morning Joe," Christie took another unprompted shot at the Kentucky senator's high-profile opposition to the National Security Agency's controversial telephone metadata collection program.

"He should be in front of hearings in front of Congress if there's another attack," Christie said.

"People are really worried about ISIS, they're worried about the threat of terrorism, and that's why what Rand Paul has done to make this country weaker and more vulnerable is a terrible thing," Christie said. "And for him to raise money off of it? It's disgraceful."

Since officially launching his presidential campaign last week, the New Jersey governor has ramped up his years-long fight with Paul over national security. The latest barbs come a little more than a month after Paul's push in the Senate helped end the federal government's bulk collection of metadata, shifting that responsibility to telephone companies.

On Sunday, Christie defended the NSA's bulk metadata collection program, and said that Paul's push to rein in the agency made US national security weaker.

“As we face a heightened warning on this Fourth of July weekend, what the American people need to know is that Senator Paul’s conduct has made them weaker and more vulnerable to attack,” Christie said on "Fox News Sunday."

The two Republicans have traded barbs over national security for years.

Christie claims that the NSA's telephone surveillance program was a necessary tool for him to prosecute terrorists as US attorney. Paul maintains that the program is unconstitutional.

In 2013, Christie said the Paulian "strain of libertarianism was "dangerous," adding that the debate over the NSA was "esoteric."

Paul's office shot back, saying that Christie was out of touch with Americans.

“If Gov. Christie believes the constitutional rights and the privacy of all Americans is ‘esoteric’, he either needs a new dictionary, or he needs to talk to more Americans, because a great number of them are concerned about the dramatic overreach of our government in recent years,” Paul's office said, according to Politico.

Watch the interview below, via MSNBC:





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