You could call them the power couple of United States foreign policy ... or perhaps, the odd couple.
Secretary of Defense Robert Gates is a Republican insider who has served eight presidents but shuns politics. Secretary of State Hillary Clinton is a Democrat and one-half of perhaps the most political couple on earth. Historically, the country's Secretary of State and Secretary of Defense have often been at each other's throats, competing for budgets, political turf and influence. Clinton and Gates say their experience has been the opposite.
"We didn't get the memo about how we were supposed to be diametrically opposite on everything," Clinton said, as she and Gates sat down with "Nightline's" Cynthia McFadden, the only joint television interview the two have ever granted abroad.
Watch the full interview on "Nightline" tonight at 11:35 p.m. ET
Clinton and Gates have formed a rare and powerful alliance. They've joined forces to become two of President Obama's most trusted advisors. In Bob Woodward's recent book, "Obama's Wars," they are referred to as two of the "blocks of granite" -- standing firm in their push for the president to add more troops in Afghanistan. This week found the pair meeting with officials in Melbourne, Australia. It's their fourth trip together this year.
Before they began working together, they didn't really know each other.
"All I knew of Hillary was what I'd seen on TV," Gates said.
Clinton knew Gates from his testimony before the Senate Armed Services Committee, which Clinton served on while in the Senate.
Gates, she said, was a change from his predecessor, Donald Rumsfeld.
"This secretary would actually answer questions. He would express his opinion," she said.
Today, the two like to share laughs about being older members of the administration.
"We have what we call the Old Folks Caucus," Gates said. ... "We're the only ones that kind of pick up on our cultural allusions and our jokes and things like that."
For Gates, old age jokes belie serious questions about his retirement. He confirmed to "Nightline" that he plans to leave his post "sometime next year."
"There is a lure in senior positions in Washington that makes you want to stay. And I think it's important and empowering to be willing to leave," he said.
Will Clinton Be the Next Defense Secretary?
Gates' close working relationship with Clinton, meanwhile, has only added fuel to what has become one of the most buzzed about parlor games in Washington: Whether Clinton will take Gates' job when he does retire.
Asked what she would do if Obama offered her the job, Clinton played coy.
"I have made it clear that I love the job I have," she said.
Gates, for his part, said he believed Clinton could do his job but added that one of her "great strengths" was being a "spokesperson for the United States around the world."
"That's not the role of the Secretary of Defense," he said.
As the subject turned to politics, Clinton was more open about her disappointment over last week's midterm elections.
"I was very sad to see a lot of good people turned out of Congress for doing the right thing," she said.
For Clinton, the elections brought back memories of 1994, when Democrats took a beating in that year's midterm elections, two years after her husband, President Bill Clinton took office.
Clinton said that the challenge after facing midterm losses is to "stay your course and your principles and do what you believe is right for the country," but present it in a way that resonates with voters.
"Bill made a lot of hard decisions for the Congress, you know, raising taxes to go down with the deficit, getting assault weapons off the streets, and a lot of other things that were very difficult. And people lost their seats in Congress because nobody understood exactly what this would all mean to the average voter," she said. "Similarly, [President Obama] inherited a terrible economic situation. I think what he's done has prevented a depression, even though I'm very worried about the fact that employment is not where it should be and the president is working hard on that. But what he has to do now is figure out ways to advance what he thinks is the right agenda for America, working with a Republican house and a narrower majority of Democrats in the senate."
Many have questioned whether Obama would move to the center in the wake of the Democrats' poor showing in the midterms, as political analysts say President Clinton did.
Hillary Clinton sees it differently.
"I don't think that Bill changed his principles or changed his objectives or really reversed course in any way," she said. "I think what he did was take a very clear-eyed assessment of what was going to be possible with the congress after the election, and moved on every front that he could to get things done. And I think that's what you'll see President Obama doing."
Gates on McChrystal: He Behaved With 'Extraordinary Integrity'
As for her own plans for Congress, the Secretary of State said she had a call into soon-to-be House Majority Leader John Boehner and said she could "absolutely" work with him.
In that work, it seems, Gates will be by her side. The soft-spoken Republican and the superstar Democrat are leaving little daylight behind them, even on the thorny issue of "don't ask, don't tell."
Both reiterated their support for allowing gays to serve openly in the military and dropping the policy -- which was instituted by the Clinton administration as a substitute for its earlier effort to end the military's ban on gay service members -- though Gates said the "smart" way to address "don't ask, don't tell" was through legislation rather than judicial means. (The 9th U.S. Circuit Court of Appeals recently ruled to keep "don't ask, don't tell" in place for now after a lower court judge declared it unconstitutional.) That process could take much longer, something President Obama has been criticized for by his base.
"This thing is gonna go one way or the other. And, you know, there's smart ways to do things and there's stupid ways to do things," Gates said. "Trying to do this all at once and under some kind of fiat, I think is not the way to do it."
While the firestorm over "don't ask, don't tell" continues to rage on, Gates seems to have put another controversy behind him: President Obama's unceremonious dismissal of Gen. Stanley McChrystal, the top U.S. commander in Afghanistan, after McChrystal and his aides slammed members of the Obama administration in an article in Rolling Stone magazine.
Gates said that while President Obama was right to fire McChrystal, he still believed that McChrystal was still "the right man" for Afghanistan. His successor, General David Petraeus, has continued work on plans that McChrystal put together, Gates said.
He said he hasn't spoken to McChrystal since his retirement.
"What happened was an unfortunate thing, a tragedy in many ways," he said.
"The truth of the matter is General McChrystal took responsibility for this on himself," Gates added. "He behaved, I thought, with extraordinary integrity."