Image copyright Getty Images Image caption Donald Trump has promised to transform the nation if elected president

Donald Trump says that if he's elected, he'll fix Washington and run the nation like a business. People here are wondering whether he'd make good on his promise. Would President Trump fix Washington - or would Washington fix him?

Trump scares the Washington Establishment, an amorphous group of lawmakers, lobbyists, journalists, lawyers and others. If he were elected, he could up-end Washington - and break things.

"He's saying he could completely overturn Washington," James Madison University's Marty Cohen said, describing Trump. "Whether he could do it or not, it's still a threat."

Not surprisingly, the nation's capital has been reeling.

"I can't think of a president who represents such a change," said Michael Kazin, the author of The Populist Persuasion: An American History.

He said the closest analogy to Trump is President Andrew Jackson, who served from 1829 to 1837.

Jackson's supporters were seen as "unruly masses", "back woodsmen who drank too much", said Kazin. After the election, they threw a party and "broke crockery".

Image copyright Getty Images Image caption First Lady Michelle Obama has expressed concern about her garden

People in Washington are worried that Trump would unleash that kind of energy - or worse.

As University of Maryland's David Karol, co-editor of a book called Nominating the President, put it: "They're horrified."

Things got tense when Trump rose in the polls. In August he came within three points of his Democratic rival, Hillary Clinton, according to Ipsos/Reuters.

She's now way ahead in polls. But the FBI has reopened its investigation into her use of a private email server. This has again raised fears among the Washington elite about a Trump victory.

At a rally in Florida earlier this month, he gave them a warning. "For those who control the levers of power in Washington, and for the global special interests," he said. He told the audience that the days of the Washington establishment were numbered.

"Our campaign represents a true existential threat like they haven't seen before," he said.

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Image caption More than a dozen Guantanamo detainees take a yoga-breathing class to deal with "stressors"

For those at the rally - and many others outside of Washington - the possibility of a Trump presidency has been invigorating.

Stephen Moore, a senior economic adviser for Trump, said he'd start a new chapter. "He's a businessman," said Moore, saying Trump would be the "CEO of America and of the federal government".

"He knows how to cut expenses and make a profit," said Moore. "The US government is a $4 trillion enterprise, and someone who knows how to run something would be a real asset."

Trump is unconventional in many ways.

Still, he falls into a tradition of the outsider-candidate.

Everyone from Jimmy Carter, a Democrat who was elected in 1976, to Ross Perot, a business executive who ran an unsuccessful campaign as an independent in 1992, has done it.

Even Barack Obama, a US senator (and consequently a Washington insider), used this approach.

"In Europe it's a different kind of system," said University of Nebraska's Elizabeth Theiss-Morse, co-author of Stealth Democracy: Americans' Beliefs About How Government Should Work.

"They don't have the same type of dysfunction. So you don't see the real frustration that Americans feel."

Image copyright Getty Images Image caption As president, Trump would get to know President Vladimir Putin better

Surveys show people in the US have little faith in political institutions, and outsider campaigns tap into the resentment Americans feel towards Washington. They see the city as a cesspool of the federal government, a symbol of bureaucracy, laziness and ineptitude.

The outsiders demand change - and often have huge popular support. "He's revealing all this stuff that people in Washington have to deal with," said Theiss-Morse.

"The perception is that government can't be trusted."

No wonder people who are in the establishment are concerned. They're worried about an array of things.

First Lady Michelle Obama is concerned about her garden.

Earlier this month, she told visitors: "I take great pride in knowing that this little garden will live on."

Trump doesn't seem to like vegetables. People are worried the garden will lay untended (or get cemented over).

The fate of Guantanamo could shift. One-third of the 60 men at the prison have been cleared to leave. But Trump said he wants to fill the prison up again with "some bad dudes".

The commander of the prison camp, Navy Rear Adm Peter Clarke, said earlier this year he wondered about the fallout from a Trump victory - and what the prisoners would do.

Image copyright Getty Images Image caption Trump's critics worry about whom he'd nominate for the Supreme Court

Once in office, Trump would learn about nuclear launch codes. Given his expansive attitude about nuclear weapons (he's said South Korea might want to consider them), some find the possibilities unsettling.

While campaigning, he's expressed admiration for President Vladimir Putin. "There's the danger of foreign policy disasters, military disasters," said Peter Wehner, a former senior advisor to President George W Bush.

Gordon Gray, the director of fiscal policy at the American Action Forum, a centre-right think tank, has looked at the budget poses: "Not good - not good at all. He would risk a recession."

During this time, according to environmentalists, the planet will heat up - and Trump will renounce the Paris agreement.

He could tear up the nuclear deal with Iran.

"You know," Karol said, and sighed. "Change to what end? The Taliban shook things up."

Who is ahead in the polls? See full poll tracker

As scholars explain, however, true revolutionaries like Trump have a hard time.

Under President Bush, Vice-President Dick Cheney and Defence Secretary Donald Rumsfeld, both of whom had already spent many years in government, knew how to pull levers.

But when you've campaigned against your own party, Kazin said, your options are limited: "Who do you appoint - Sarah Palin as secretary of the interior?"

He added: "The established power structures have a way of disciplining the person."

Cohen said: "A lot of people go to Washington, and they end up changing, and Washington ends up staying the same."

He and others said that real change is done through institutional reform such as campaign finance and term limits. They agreed that these changes are unlikely to be carried out by the people who are here.

"Reform a system that serves them well?" Cohen said. "The people that are going to decide these things are the people who are benefiting from them."

They say that regardless of who's elected in November, the Washington elite will remain - the Washington elite.

Follow @Tara_Mckelvey on Twitter.

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