THE night of the 2016 U.S. presidential election, Robert O’Brien, a fixture of Republican presidential campaigns for more than a dozen years, was in London, glued to television screens with American visitors and Brits alike.

“I’m not sure anybody out there predicted a Trump win,” he said several days later. “I certainly didn’t.”

O’Brien, 53, who served as a foreign policy adviser for the failed presidential campaign of Wisconsin Governor Scott Walker, then for that of Texas Senator Ted Cruz, never endorsed Donald Trump in 2016. But on Wednesday, the U.S. president picked O’Brien, the State Department’s top hostage negotiator, as his fourth national security adviser.

“It’s really a role that, if the president respects the person that’s the adviser, I think it really plays a very, very important role,” Trump said. “I have worked long and hard with Robert. He will do a great job!”

Whether O’Brien, a diplomat who has served in both Republican and Democratic administrations, can fit that role is far from clear.

The hostage negotiator enjoyed support from Secretary of State Mike Pompeo, who is now the most influential national security voice in the administration.

John Bolton, by contrast, was a highly controversial figure in Washington. His instincts for an aggressive, interventionist foreign policy were at odds with Trump’s more isolationist stance.

Bolton “wasn’t getting along with people in the administration who I consider very important” and “wasn’t in line with what we were doing,” Trump said.

O’Brien does not appear to have that problem. “I think we have a very good chemistry together,” Trump said.

A longtime lawyer and foreign policy adviser to Republicans, O’Brien has become one of Trump’s favorites for his work on behalf of Americans held prisoner in places including North Korea and Turkey.

Trump said his work had been “unparalleled” and “tremendous.”

While such cases are termed “hostages” by Trump, this is far from always true. In the most unusual episode, O’Brien was dispatched to U.S. ally Sweden to attend the trial of U.S. rapper ASAP Rocky, who was accused of assault.

Although Bolton was seen as the ultimate representative of the neo-con wing in the Republican party, cheering for war in Iraq and pushing for regime change in Iran, O’Brien will bring his own hard edge to foreign policy.

In his 2016 book “While America Slept,” O’Brien criticized what he called then-outgoing President Barack Obama’s attempt to present a more collaborative, dovish United States.

This meant “autocrats, tyrants and terrorists were emboldened,” he argued.

“In the face of rising challenges around the world, it is time to return to a national security policy based on ‘peace through strength,’” he wrote.

“A strong America will be a nation that our allies will trust and our adversaries will not dare test.”

O’Brien will find a stacked in-tray waiting for him at the White House, with Iran at the top of the pile.

While there are loud voices in Washington calling for the bombing of Iran following the Saudi oil facility strikes, Trump’s instinct so far has been to resist expanding U.S. foreign military entanglements.

Another vexing item for Trump is Afghanistan, where he has repeatedly said he wants to wind down the two-decade U.S. military presence.

Peace talks with the Taliban and a surprise planned meeting between the insurgents and Trump himself, something apparently opposed by Bolton, were scrapped earlier this month.

Trump, who is known to respond well to flattery, has recounted praise from O’Brien in tweets and in conversations, suggesting that the new national security adviser also knows how to handle the president and his mercurial moods.

O’Brien has also made Trump look good — giving him numbers to boast about and successes that made for high profile media coverage.

Speaking to reporters aboard Air Force One on Tuesday, Trump again highlighted O’Brien’s praise of him in securing the release of hostages.

“Robert O’Brien said, ‘Trump is the greatest hostage negotiator in history.’ He happens to be right,” Trump said, according to pool reporters. “We are 38-0. Thirty-eight-0, ask Robert. In fact, I had never heard the term. Robert O’Brien said Donald Trump is the greatest hostage negotiator of all time.”

The State Department has given further details on the numbers cited by Trump.

During an Oval Office meeting in March, O’Brien celebrated Trump for his success returning American hostages.

“This wouldn’t happen with all of these hostages and detainees without the support of the president,” he said. “The president has had unparalleled success in bringing Americans home without paying concessions.”

One senior White House official argued the pick shows that Trump “wants a consensus builder, not a showboater” in the role, suggesting O’Brien will cut a lower profile and work better with others in the administration than Bolton did.

O’Brien, though, has far less national security or foreign policy experience than past national security advisers — under Trump or otherwise. CNN previously reported that the national security adviser role was expected to be diminished in the wake of Bolton’s departure as Trump increasingly relies on his own instincts.

Born in Los Angeles, O’Brien attended high school in Santa Rosa and then attended UCLA. Shortly after completing law school at UC Berkeley and passing the California bar, O’Brien joined the Army Reserve Judge Advocate General Corps and launched his civilian law career, he said in a 2015 interview.

He moved to La Canada Flintridge decades ago and raised two children there. His son Robert died in an accidental drowning in September 2015, a few months after his high school graduation.

O’Brien left the Army Reserve as a major in 2005, but his service led to work with the United Nations Security Council from 1996 to 1998, where he helped review billions of U.S. dollars in claims from Iraq’s 1990 invasion of Kuwait, which prompted the U.S.-led Persian Gulf War in 1991.

Later, he served four years on a State Department committee trying to reform the judicial system in Afghanistan, starting under President George W. Bush and finishing under President Obama.

He has long backed the mainstream Republicans that Trump disdains. After advising now-Sen. Mitt Romney, a fellow Mormon, in his failed 2008 and 2012 presidential runs, O’Brien worked for Walker, one of the first candidates to drop out in 2016, and then Cruz, ultimately Trump’s runner-up for the Republican nomination.

O’Brien is the co-founding partner of Larson O’Brien LLP in Los Angeles, a litigation firm. In addition to his client work, O’Brien served as an arbitrator in international proceedings and was appointed by federal courts to serve as a special master in numerous complex cases.

O’Brien sees himself as a Reagan Republican, and he supported Trump’s campaign promises to “rebuild the military.” Still, when Trump emerged as the likely Republican nominee, O’Brien expressed reservations about his national security prowess.

“Unfortunately, he has been short on specifics and has criticized key weapons systems,” he said at the time.

Yet O’Brien didn’t join the “Never Trump” movement founded by some Republican former national security officials and analysts, keeping his options open.

After the election, O’Brien suggested that Trump’s tough language against adversaries like Iran, as well as allies from NATO members to Japan, was yielding results.

“My perception of Mr. Trump is that he’s a negotiator,” O’Brien said then. “It’s the first time in my lifetime that I can recall having very serious conversations [with Europeans] about increasing defense spending, about Russians being on the doorstep. … Trump’s isn’t just rhetoric. They know they better take some steps.”

“I think Robert is low-drama, but I would not interpret that as being weak,” said Pierre-Richard Prosper, who was ambassador-at-large for war crimes in the George W. Bush administration and who’s known O’Brien for more than 25 years. “He’s a strong person and confident in his views. ... On foreign policy and the role of the United States in the world, those remain consistent.”

“He understands the world for the dangerous place it is,” said Sen. Lindsey Graham, who also knows O’Brien.

Days after Trump won, O’Brien predicted that he would “grow into” the presidency.

“There’s a lot of rhetoric that takes place in the campaign, but the president is constrained by the constitution and the court,” O’Brien said. “For the most part, American presidents grow into the job. I have no doubt Donald Trump will grow into the office.”(SD-Agencies)