ANALYSIS: One year in, Donald Trump has redefined the presidency

Tweet it out, put on "tapes," or just let the cameras roll. There will be a clear historical dividing line that separates what the American presidency and American politics were on either side of the current occupant of the Oval Office.

That's the unmistakable conclusion one year into the entirely unconventional and enormously consequential presidency of Donald J. Trump.

Trump has fundamentally remade the office and how it functions, often on the fly, and generally in ways that he alone could have envisioned or executed. His instincts - to fight, to divide, to disrupt, to insult - have redefined what it means to be presidential.

There will surely never be another Donald Trump. But neither can there be a wholesale reversion to what the office he holds was like before he assumed it.

"He brought a whole new rambunctious, freewheeling style to the presidency that won't go away," said Julian Zelizer, a history professor at Princeton University.

"He keeps doing things that other presidents didn't do, and that we assumed they couldn't do," Zelizer added. "There's no need to presume the next president will be like Trump. But now it's all on the table."

The first year of the Trump presidency has alternated formats between reality show, civics lesson, comedy, and - depending on your point of view - tragedy. It's been part "Veep," part "House of Cards," part "24," with the president occasionally trying to stage scenes out of "The West Wing."

It has featured a president constantly pushing boundaries and prodding institutions, not just defying conventions but smashing them. He's been offensive, shocking, and sometimes seemingly self-destructive - but he's also getting things done in ways both small and profoundly large.

"Instinctively, he's trying to grab each cage and shake it," said John H. Sununu, a former New Hampshire governor and White House chief of staff under President George H.W. Bush.

Sununu opposed Trump during the primaries, but now says he is accomplishing conservative priorities and remaking the office in what he views as largely positive ways, in line with a changing media environment.

"What he did in his campaign was found a way to connect with everybody who had angst," Sununu continued. "What he's doing now as president is trying to deal with the institutions that gave everybody heartburn."

His supporters applaud it all as authenticity. They argue that the American people elected the long-running star of "The Apprentice" precisely because he would shatter calcified traditions.

It's that entertainment mentality - the president himself often brags of his "performance" and "reviews," and just last week welcomed reporters to his "studio" inside the White House - that runs as a colorful through-line for Trump's time in office.

Yet, in that spirit, Trump has veered the political debate between fiction and non-fiction with startling and unprecedented regularity. Other presidents have lied, or otherwise intentionally misled the public. But Trump has displayed a casual indifference to the truth that has no precedent in public life.

"He's willing to say things that are not true," said Zelizer, the Princeton historian. "He just does it. Even when he's told he's doing it, he's going to continue to do it."

The Washington Post has tallied 2,000 false or misleading public statement from the president over his first year in office. They've ranged from trivial claims about his own poll numbers and crowd sizes to precedent-busting - and potentially legally actionable - false critiques of the special counsel's investigation, his vanquished opponent, and even his predecessor in the White House.

Then there are the insults. Various opponents and even some allies have been "psycho," "weak and out of control," "totally unhinged," "short and fat," "sleazy," and - perhaps most famously - "crooked." Just last week, in an Oval Office meeting with a group of senators, he was reported to have referred to nations including Haiti as "s---hole countries."

The casual, profane nature of Trump's communication style - punctuated by his use of Twitter for offhand observations, incomplete policy announcements, and reactions to cable television - is part of how he's sought to make himself the star of a show where the prequels weren't required viewing.

In describing Trump's decision-making style, White House chief of staff John Kelly told The New York Times recently there was one thing he noticed Trump not doing: "He very seldom asks how other presidents did this."

His freewheeling, convention-defying style has extended into the realm of foreign policy. There have been Twitter taunts of North Korea's nuclear-armed dictator, provocations aimed at powerful friends like Great Britain and frenemies like China, and quick actions to move embassies, cancel trips, and remove the United States from multinational treaties.

Decades of bipartisan precedents have been broken along the way. The consequences for war and peace are vast, though Trump has betrayed little concern over that, or any trepidation about how his bellicose words will be received.

Likewise, on the domestic front, Trump has positioned himself as the main player in a not-always-amusing drama. He warred with powerful forces inside his own party through much of a frustrating 2017, only to close out the year with kind of tax deal perhaps only Trump - with his mastery of messaging - could have achieved, according to Sununu.

"He's ordering the daily agenda," Sununu said. "That's a very, very significant thing. He could not have gotten tax reform had he not controlled the way tax reform was being tossed about."

In a critical sense, Trump has governed as he campaigned - as a celebrity who understands the intersection of modern media and American culture and sees politics as an extension of both.

He has sought to take advantage of the nation's short-attention span and its general mistrust for institutions and politics as usual. He has tried to make a politics a reflection of his own aggressive, often boorish and crude, personality.

But while Trump has redefined the job, his success or failures in office may be defined by what he has been unable to change.

The judiciary and even Trump's own federal bureaucracy and military apparatus have served as checks on presidential impulses, resisting his efforts to rewrite laws and create his own realities. The president's cries of "fake news" notwithstanding, the news media remains a powerful and independent force, even in the age of "alternative facts."

Even with Republican control of Congress, lawmakers have established some limits to Trump's powers in both domestic and foreign policies. Republican control, of course, may not last Trump's entire first term, with an empowered and energized "resistance" movement fueling 2018 midterm campaigns in reaction to the president and his brand of leadership.

Looming over all: A special counsel's investigation of Trump's campaign and Russia's election meddling churns along. That's mechanism that could snap the presidency back toward established norms, depending on what is learned - created in part by Trump's rash move to fire the director of the FBI, James Comey, in the midst of his own investigation on the subject.

It will likely take decades to determine the true impact of the Trump years, as with any presidency. But the president has already revealed important truths about the nation that put him in office.

"He's showing what we've built - exactly the system we created," Zelizer, the Princeton historian, said. "He has exposed how powerful the presidency can be."

This story is part of a week-long series examining the first year of the Trump administration.