WASHINGTON — Donald Trump enters the White House on Friday just as he entered the race for president: defiant, unfiltered, unbound by tradition and utterly confident in his chosen course.

In the 10 weeks since his surprise election as the nation’s 45th president, Trump has violated decades of established diplomatic protocol, sent shockwaves through business boardrooms, tested long-standing ethics rules and continued his combative style of replying to any slight with a personal attack — on Twitter and in person.

Past presidents have described walking into the Oval Office for the first time as a humbling experience, one that in an instant makes clear the weight of their new role as caretaker of the American democracy. Trump spent much of his transition making clear he sees things differently: Rather than change for the office, he argues, the office will change for him.

“They say it’s not presidential to call up these massive leaders of business,” Trump told a crowd in Indianapolis in December after he negotiated a deal with an air conditioning company to keep jobs in the state. That was a move many economists derided as unworkable national economic policy.

“I think it’s very presidential,” he declared. “And if it’s not presidential, that’s OK. That’s OK. Because I actually like doing it.”

Even before he takes the oath of office, Trump has changed the very nature of the presidency, breaking conventions and upending expectations for the leader of the free world.

Advisers who’ve spoken with Trump say the billionaire real estate mogul and reality TV star is aware of the historic nature of his new job. He’s told friends that he’s drawn to the ambition of Ronald Reagan, a Republican, and John F. Kennedy, a Democrat. He’s thinking of spending his first night in the White House sleeping in the Lincoln Bedroom, according some who dined with him recently in Florida.

But Trump also views himself as a kind of “sui generis” president, beholden to no one for his success and modeling himself after no leader who’s come before. He has said he’s read no biographies of former presidents. When asked to name his personal heroes in a recent interview, he mentioned his father before replying that he didn’t “like the concept of heroes.”

“I don’t think Trump has a great sense of the history of the White House. When you don’t know your history, it’s hard to fully respect the traditions,” said historian Douglas Brinkley, who recently dined with Trump and other guests at his South Florida club. “This is not somebody who brags about how many history biographies he’s read.”

“He’s somebody who brags about it as this is a big event and he’s the maestro.”

That’s a shift that thrills his supporters, who elected Trump to shake up what they see as an unresponsive and corrupt federal government in the “swamp” of Washington.

“I don’t want him to change,” said Iowa state Sen. Brad Zaun, one of Trump’s earliest backers. “One of the reasons that I supported him is that he told it the way it was. He didn’t beat around the bush. He didn’t do the standard political talking points.”

Trump won election with that approach, but he’s yet to win over the country. His Electoral College victory was tempered by a loss in the popular vote to Democratic nominee Hillary Clinton by nearly 3 million ballots. The protests planned for the day after his inauguration threaten to draw more people to the National Mall than his official events.

Polls over the past week show that Trump is poised to enter the White House as the least popular president in four decades. Democrats remain staunchly opposed to him, independents have not rallied behind him and even Republicans are less enthusiastic than might be expected, according to the surveys.

In his typical reaction to poll results he doesn’t like, Trump dismissed them as “rigged” in a Tuesday tweet.

That no-holds-barred approach has served him well as the CEO of a family corporation, who has no oversight from a corporate board or shareholders. But a president is constrained by a system of checks and balances. Former Cabinet officials say the layers of government bureaucracy, myriad regulations and intricacies of Congress will challenge Trump’s style.

“A president doesn’t have sweeping, universal authority. It is a very different operation than being a CEO who can fire people and hire people at will,” said Kathleen Sebelius, a Democrat and former health and human services secretary. “He’s never been part of any organization with a framework where institutional rules are in place.”

But Trump’s supporters say it’s the institutions and Washington — and not the next president — that must change.

“Trump believes that he has a better understanding of how things work in the modern world than all of these so-called critics,” said Newt Gingrich, a Trump adviser and former Republican House speaker, who has spoken with the president-elect about his presidency. “That’s who he is.

“The rest of us are going to have to learn how to think through that.”