WASHINGTON -- An increasingly rare thing happened earlier this month on Capitol Hill.

Former Georgia U.S. Sen. Sam Nunn, a Democrat, took to the witness stand twice in two days to vouch for a pair of Cabinet nominees nominated by a Republican president.

A modest gesture, yes. Notable in this radioactive political environment, for sure -- especially given that we're talking about a four-term senator who once called Donald Trump "an apprentice in the nuclear arena" with a "colossal ego" and "no appetite for learning."

Nunn in a recent interview said he stands by his past assessment of Trump when it comes to nuclear weapons, the topic to which he's devoted his post-Senate career. And he thinks Trump's advisers need to change his Twitter password.

But the Hillary Clinton supporter said he felt compelled to testify on behalf of Rex Tillerson and James Mattis, the president's picks for secretary of state and defense, after they separately asked him to earlier this month.

“I didn’t have really any hesitancy,” he said. “I think the president needs the best Cabinet people he can. We have a lot less checks and balances in the foreign policy and security arena than we do on the domestic side, so I think the two appointments …  to me are the most important, particularly for a new president who has not had the experience.”

Nunn said he's concerned that bipartisanship on Capitol Hill has gotten considerably worse since he left 20 years ago.

“I’d never passed a very significant piece of legislation without a Republican partner, and somehow we’ve got to get back to that,” he said. “It doesn’t mean you agree on everything but civility is at the heart of it.”

The limits of that civility are currently getting tested as the Senate considers Trump's Cabinet nominees. Republicans are accusing Democrats of slow-walking the confirmation process in order to obstruct Trump's effectiveness as president. Democrats argue Republicans are racing through the consideration process without proper vetting.

The Senate so far has approved only two of Trump's nominees. (Mattis is one of them.) Tillerson is expected to be confirmed in the days or weeks ahead after Florida Republican Marco Rubio indicated he would support the former ExxonMobil CEO on Monday.

Nunn attributes the hyper-partisanship on Capitol Hill to a variety of factors, from constant fundraising and travel to cable television, but said he hopes the two sides can find a way to work together in the best interest of the country.

As for Trump, he said he hopes Mattis and Tillerson can help the new president when it comes to nuclear weapons.

"I do think he has a lot to learn and I hope he’s developed an appetite for learning," he said.

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