Sen. Rand Paul might have reclaimed some of his lost libertarian luster during a heated exchange with Chris Christie over the constitutionality of the NSA's phone records collection program.

The fight started after Christie asserted that Paul was wrong to raise civil liberties concerns about NSA spying.

"I will make no apologies ever for protecting the lives and the safety of the American people," said Christie. "We need to give more tools to our folks to be able to do that, not fewer, and then trust those people and oversee them to do it the right way. As president, that's exactly what I will do."

Paul shot back immediately.

"I want to collect more records from terrorists, but less records from innocent Americans," said Paul. "The Fourth Amendment was what we fought the Revolution over. John Adams said it was the spark that led to our War for Independence. I'm proud of standing for the Bill of Rights and I will continue to stand for the Bill of Rights."

Christie insisted that Paul had given a "ridiculous" answer, since there is no way to tell the terrorists apart from the innocent American citizens. Paul responded that the way to discern the difference is to ask a judge for a warrant.

"I'm talking about searches, without warrants, indiscriminately of all American's records, and that's what I fought to end," said Paul. "I don't trust President Obama with our records. I know you gave him a big hug, and if you want to give him a big hug again, go right ahead."

Christie cited 9/11 in response (for at least the second time).

"The hugs that I remember are the hugs I gave to the families who lost their people on September 11th," he said. "Those are the hugs I remember."

Paul could not help but roll his eyes.

Christie is a big government bully who is quick to play the 9/11 card—and he's not alone on the stage in that regard. Paul's best way to distinguish himself from the rest of the field is to shore up his credentials as a defender of the liberties of all Americans, and taking on Christie was an excellent way to do that. It's important to remember that plenty of Republican primary voters—and indeed, plenty of Americans, period—are extremely uncomfortable ceding unchecked surveillance powers to the federal government.