For Marco Rubio, the easy part is over. He was confirmed by the Senate as secretary of state with unanimous support, Democrats joining Republicans in praising his acumen and judgment.

Now comes the task that will make or break his tenure: retaining the full backing of his new boss, Donald Trump.

The 53-year-old Rubio is coming into the job with more experience than President Trump’s previous secretaries of state, having spent the last 14 years in the Senate becoming intimately acquainted with U.S. foreign policy from the Indo-Pacific to the Middle East and Latin America. But that traditional experience, coupled with Rubio’s longstanding hawkish views on Russia and support for America’s role in NATO, is what some worry will eventually make him the target of Trump’s wrath.

“Rubio is going to face some challenges as he and the president try to come to terms about what is the purpose of American power?” said Thomas Shannon, a former U.S. diplomat, who often worked with Rubio during both the Obama and the first Trump administrations.

Still, it was a collegial scene Tuesday as Rubio was sworn into office. Vice President JD Vance, who served alongside him in the Senate, called him a friend and a “bipartisan solutions seeker” as he delivered the oath.

Rubio echoed Trump in his own brief remarks, emphasizing that anything the government and State Department do must make the country stronger, safer or more prosperous.

“If it doesn’t do one of those three things, we will not do it,” Rubio said.

He repeated that sentiment as he made his first appearance at the State Department, telling staffers that his job, and theirs, would be to defend and execute Trump’s “America First” policies.

Rubio’s support in Washington has an establishment tinge, with many hopeful he will prove a steady hand at a time of global upheaval. In interviews with more than a dozen people, including Republican and Democratic lawmakers, as well as former diplomats and colleagues, he was repeatedly described as the “responsible” choice to represent the U.S. abroad, a known quantity both at home and on the global stage.

“I think he’ll be able to deliver that message, country by country, continent by continent, and that’s uncompromising, but also that’s comforting,” said Sen. Kevin Cramer, a Republican from North Dakota. “Not that I’m looking for every other country to be comfortable with us, but in a way that I think is not alarming.”

Rubio’s worldview has been largely shaped by his own history: the son of Cuban immigrants who arrived in Miami in May 1956 “with nothing but the dream of a better life,» he testified before the Senate Foreign Relations Committee last week. His father was a bartender and his mother a hotel maid.

“Because of them, I had the privilege to be born a citizen of the greatest nation in the history of the world,” he said. “And to be raised in a safe and stable home, by parents who made their children’s future the very purpose of their lives.”

The “only in America” story is one that helped him get elected to public office in Florida, making his way from city commissioner to the Florida House of Representatives, eventually becoming the first Cuban American speaker in the Legislature’s history.

When Rubio became speaker, “it was a very big deal. I think the ceremony was projected towards Cuba, whether they wanted to hear it or not,” said Dan Gelber, who served as Democratic leader at the same time. He said that he and Rubio remained friends over the years despite “severe disagreements about policy.»

«He was never a jerk. He was always respectful of the process and our voice,» Gelber said. “It was sort of the way I always thought a partisan government should operate.”

Rubio’s rise continued in 2010 as he was elected to the Senate as part of the “tea party” wave of outsiders taking on Washington. His first Senate speech focused on the “American miracle» that brings immigrants from all around the world to the U.S. to “leave their children better off then themselves.”

A few years later, he was part of a bipartisan group that advocated for allowing a path to citizenship for immigrants in the country illegally. He played a key role in crafting a sweeping, bipartisan immigration bill that passed the Senate but went nowhere in the House, defeated by a fierce conservative backlash.

In the decade since, Rubio’s views on immigration have shifted toward the hard-line stance of Trump, who on Monday made good on his campaign pledge to aggressively pursue deportations and restrict entry into the United States in his second term.

In his confirmation hearing, Rubio echoed Trump’s dark vision of America’s immigration system, saying that “despots and narco-terrorists» have taken advantage of «open borders to drive mass migration, traffic women and children, and flood our communities with fentanyl and violent criminals.»

It was a remarkable tone for Rubio, who is working overtime to ensure there is no daylight between his public statements and Trump’s. While his colleagues across the aisle believe that he is conforming to Trump’s rhetoric, they’re hopeful he will maintain some of his mainstream views.

«I think Marco is a hawk, but he’s also an internationalist, and I think the challenge for him will be to maintain the long bipartisan tradition of America being indispensable in world affairs,” said Sen. Brian Schatz, a Hawaii Democrat who served with Rubio on the Foreign Relations Committee. “And there are people in the Trump world who want us to run away from being the leaders of the free world. And I’m hoping that Marco’s instincts towards American strength will win the day.”

Both sides agree that it will be Trump who decides if Rubio is MAGA enough to remain a member of his administration and represent his views around the world. He unceremoniously fired his first secretary of State, Rex Tillerson, via tweet, and has long made clear he views foreign policy as his domain.

Rubio is also no stranger to Trump’s fury. The two men exchanged schoolyard jabs during the 2016 Republican primary with the president labeling him “little Marco.” Rubio responded by insulting the size of Trump’s hands and calling him a “con artist” and “vulgar.»

Asked if he believes Rubio can last in the job, Rep. Michael McCaul, who until recently served as chairman of the House Foreign Affairs Committee, gave a nod to past turmoil.

“Well, it is the Trump administration,» McCaul said. «But I think he’s a survivor.”