But now the two may find that they have some key goals in common that could forge the kind of unlikely marriage that only exists in Washington, where political expediency can turn enemies into allies almost overnight.

Trump, of course, is now president-elect. McCain, himself a former Republican presidential nominee, chairs the Senate Armed Services Committee. While they are far apart on issues such as torture and Russia, they share common ground over how the Pentagon does business. Both want to grow the military. Both want to shake up the Pentagon bureaucracy. And both have taken aim at major programs that have gone wildly over budget and years behind schedule.

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How they get along — or don’t — could have significant impacts for national security, the defense industry and the Washington region, where many of the largest firms are located.

After months of acrimony, it may take time for the pair to come to anything resembling reconciliation. Trump insulted McCain’s military record, saying he was no war hero for being captured during the Vietnam War. McCain lashed back after the infamous video capturing Trump making lewd comments about women, and rescinded his endorsement of the GOP nominee, saying it was “impossible to continue to offer even conditional support for his candidacy.

But now they need each other to accomplish their goals, analysts said.

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“They have every incentive to work together,” said Andrew Hunter, a defense analyst at the Center for Strategic and International Studies. “The question is can they?”

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Neither Trump nor McCain’s teams responded to requests for comment.

Both have tempers and outsized personalities that can be driven by emotion. And after a vitriolic campaign it’s not clear “if they will mend the personal distance between them. There were some very rough things said,” said Daniel Goure, a national security analyst at the Lexington Institute. “But they’ve got real interest in working together. McCain really wants to see major change and major accomplishment and make his mark on defense and national security policy. He has as much interest as the president elect would in working together.”

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While little about his policies are known, Trump has spoken in general terms of wanting to bolster the military and cut red tape at the Pentagon. To do that, his proposals would have go to through the committee McCain chairs with gusto. The former Naval officer is known for using his perch to excoriate generals, contractors, administration officials, turning his high dudgeon into some of Capitol Hill’s best theater.

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He’s taken particular aim at major weapons programs — such as the F-35 Joint Strike Fighter — that have gone over budget. And for the past few years, he’s been involved in a massive effort to reform the way the Pentagon buys everything from weapons to services.

He’s also proposed breaking up the Pentagon department in charge of buying major weapons programs to streamline it. And he’s proposed reducing the number of generals that he says makes the military top heavy. Those are the kind of bold, disruptive plans that might appeal to Trump, analysts said.

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Trump has said he wants to increase the size of the Army and the Marine Corps, build new ships for the Navy and add jets to the Air Force’s arsenal and modernize the nuclear arsenal. Mackenzie Eaglen, a defense analyst with the American Enterprise Institute, has calculated that the campaign promises could add up to an additional $55 billion in defense spending — at least.

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Trump would need McCain, then, to help push through the programs and overcome the objections of conservatives who want to trim spending.

They are, however, far apart on other matters, such as foreign policy, that could strain the relationship. McCain is a harsh critic of Russia and its president Vladimir Putin, whom Trump has praised. On torture, Trump has said he would use water boarding and “much worse” on terrorists.

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“Senator McCain has been a staunch opponent of torture and challenged the Bush Administration repeatedly and decisively on this issue,” Hunter said. “This issue has the potential to be defining in their relationship.”

Still, there is enough common ground to forge a consensus, said Richard Fontaine, the president of the Center for New American Security, who previously served as a foreign policy adviser to McCain.

“I think they can overcome those differences,” he said. “The whole point of 2017 is going to be overcoming personal and political differences so we can get something done.”