NEW YORK (Reuters) – It has proven one of Donald Trump’s greatest strengths in building a worldwide luxury brand: An obsessive attention to detail, down to the curtains hanging in hotel rooms and the marble lining the lobby floor.

As president, it may prove one of his major liabilities, presidential historians warn.

Interviews with a dozen people familiar with how Trump conducts business reveal the president-elect as a micromanager who regularly spars over details about decor in projects across his real estate and branding empire.

“I’m very much involved in the details,” Trump said during a June deposition in a lawsuit stemming from his development of a Washington hotel. “I was involved in the design of the building and the room sizes and the entrances and the lobby and the marble and the bathrooms and the fixtures and the bars and a lot of things.”

Trump announced on Wednesday that he would leave his businesses “in total” so that he could focus on the presidency. But those who have worked with him say a lifetime habit of micromanaging may be difficult to break, providing ammunition for critics who say his decisions as president will be driven by his private interests.

A former employee of the Trump Organization who has worked closely with Trump was skeptical that he could leave behind his beloved company after spending decades building it up. “I can’t picture him stepping aside for the presidency,” the ex-employee said.

Even if he does make a clean break, Trump will have to guard against getting bogged down in the bureaucratic minutiae inherent in the office. He should avoid the example of President Jimmy Carter, another famous micromanager, who spent his first months in office poring over the White House tennis court schedule, said Ross Baker, a professor of political science at Rutgers University.

Micromanagers rarely make successful presidents, said Rick Ghere, an associate professor of political science at the University of Dayton in Ohio. To be effective, presidents must delegate authority to members of their cabinet and rely on a range of expertise, he said.

“Being a decisionmaker in a high-level public position is a lot different than being a CEO,” Ghere said.

RUINED WINDOWS

Trump has said he will turn the Trump Organization over to his three adult children, who are already deeply involved in real estate projects around the world.

His daughter Ivanka, for instance, was charged with overseeing the renovation of Washington’s Old Post Office Pavilion, a $200 million project to turn the historic building into a luxury hotel. In cases where Trump has delegated authority, he still demonstrates a deep reluctance to let go, even when it comes to seemingly trivial details.

Two people who participated in an inspection of the Washington hotel with Trump shortly before he announced his candidacy in June 2015 remember the businessman growing incensed over a detail: The restoration of exterior windows.

Trump said the windows looked terrible, though one of the sources recounting the story said there didn’t seem to be anything obviously wrong with them. He demanded the contractor not be paid but was told the work had been done for free in the hopes of getting more business from the Trumps, according to the source.

That source and two others on the project also recalled hearing Ivanka say she needed her father’s approval before signing off on some decisions she wanted to make on the project. The sources said it was not uncommon for her to say she would “run this by my father” or “check with New York.”

Trump spokeswoman Hope Hicks said Trump is “incredibly detail oriented as any great developer is, something he shares with his adult children including Ivanka.”

Trump’s reluctance to step aside from his company was apparent in a New York Times interview last week in which he said, “in theory I could run my business perfectly, and then run the country perfectly.”

HOW TALL ARE THE TREES?

Trump’s reputation as a micromanager dates back to some of his earliest building projects.

In her 2013 book ‘All Alone on the 68th Floor’, Barbara Res, who oversaw construction of Trump Tower in Manhattan, described her boss in 1983 agonizing over the height and thickness of decorative trees in the building’s atrium.

Three decades later, Trump would bring his management style to the presidential campaign trail. Three sources who worked on the campaign said Trump made almost all the decisions on spending, strategy, and messaging.

According to the sources, senior campaign officials were desperate to get aboard the candidate’s plane early on in the presidential race, fearful if they were left behind he would change course on strategy and they would be shut out.

When Paul Manafort, who was helping run Trump’s campaign, secured the candidate’s authorization to spend $20 million hiring field operatives, he was triumphant, according to a Republican National Committee member, recounting an RNC meeting with Manafort in April.

The committee member though was perplexed – why had Manafort needed Trump’s approval for an expenditure on such an essential part of his campaign, and why was the amount so small? At that point in an election year, past candidates had already begun spending upwards of $80 million on the same thing.

Manafort told Reuters that while it was true most candidates simply signed off on a budget rather than reviewing each expenditure, Trump was different because he was partly funding his campaign. “I understood it and totally agreed with that approach,” Manafort said.

Later in the campaign, Trump was still agonizing over details. In October, he insisted on reviewing the script of a radio ad that was to be broadcast on stations with predominantly black audiences, according to a source inside the campaign.

Micromanaging is not necessarily a recipe for disaster – presidents like Abraham Lincoln, Carter and Barack Obama gained reputations as micromanagers, said Nancy Koehn, a professor at Harvard Business School who studies the history of leadership in the United States.

But Koehn said a micromanager with a lack of any government experience was a potentially toxic combination.

“I think it is highly likely that diving into areas in which he has very little experience without an extraordinary cast of experts around him will result in poor policy decisions which will have large unintended consequences,” she said.

Only two of Trump’s nominees so far have U.S. federal executive branch experience, although the lineup does include a state governor, several U.S. lawmakers, and a former Goldman Sachs executive.

(Reporting By Emily Flitter, editing by Paul Thomasch and Ross Colvin)

IMAGE: U.S. Republican presidential nominee Donald Trump holds a Hispanic Town Hall meeting with supporters in Miami, Florida, U.S. September 27, 2016. REUTERS/Jonathan Ernst