GOP presidential candidate Donald Trump, shown here in Scotland in 2010, is visiting the country again this week to visit two of his golf developments, an example of the blurry line between his campaign and his business interests. (David Moir/Reuters)

— All the rooms are booked here at the Trump Turnberry resort, along with all the nearby hotels and inns, as political reporters and local ­curiosity-seekers descend on this quiet, rural corner of this small country for the arrival of Donald Trump.

On Friday, police and antiterrorism agents plan to surround this resort on Scotland’s rugged west coast, where Trump plans to arrive by helicopter with his family and U.S. Secret Service agents, take questions from reporters and cut a ribbon. He will then travel to another golf course he owns along Scotland’s east coast, taking the media and security entourage with him.

The country’s top leaders, embroiled in Thursday’s historic ­Brexit vote, have declined to attend either event. Trump also has not scheduled any private meetings with government officials or any discussion of foreign policy, the activities usually associated with a presidential candidate trip overseas.

Instead, Trump will promote Trump. The two-day trip to two courses in the United Kingdom — both of which are losing money — provides yet another example of Trump using his political position to promote his personal brand.

The journey is the latest example of the fuzzy, and sometimes invisible, line between Trump the presumptive GOP nominee and Trump the businessman — an arrangement that many ethics experts, including many fellow Republicans, view as inappropriate or worse. They say Trump should take formal steps to separate himself from his business and financial holdings, both domestic and foreign, as he seeks to enter the White House, just as Mitt Romney and other candidates have done.

Republican candidate Donald Trump, shown here in Scotland in 2011, is visiting the country again this week to visit his two golf resorts, an example of the blurry line between his campaign and his business interests. (David Moir/Reuters)

“You can’t run for national office and have financial entanglements like this,” said former elections enforcement official Ken Gross, who has advised presidential candidates from both parties and who says Trump should resign from all board positions and cease day-to-day involvement running his companies.

The mogul held his announcement speech a year ago in the atrium of Trump Tower, the Manhattan skyscraper that bears his name, and has hosted a series of campaign events at properties he owns in New York and Florida, reimbursing his companies with campaign funds that largely come from his own pocket. At a campaign event at the Trump National Golf Club in Jupiter, Fla., he showed off Trump brand products such as water, wine and steaks — though the latter weren’t actually his.

Late last month, Trump used a political rally in San Diego to attack a federal judge there who is considering a multimillion-dollar fraud suit against his ­now-shuttered Trump University.

Particularly worrisome to some critics are many of the policies that Trump has advocated that could also benefit him financially. For example, he speaks glowingly about Russian President Vladi­mir Putin and vows to have warmer relations with Russia if he becomes president — a move that could help his long-standing ambition to develop properties there. Several of Trump’s campaign advisers also have had significant investments in Russia and the former Soviet Union.

These and other examples of Trump’s mingling of the political and the personal have set off alarms among ethics experts across the political spectrum.

Richard Painter, White House ethics adviser to President George W. Bush, said Trump should place his investments in a holding company and prepare to sell his interest if he becomes president.

“I am most concerned about the amount of money he and his companies owe to domestic and foreign banks,” Painter added. “That puts him in a position of being beholden.”

A doorman stands as people walk past the Trump Tower in New York. (Carlo Allegri/Reuters)

Painter said he would also advise presumptive Democratic nominee Hillary Clinton and her family to separate themselves from the global charitable foundation that bears their name, although he said the issues facing the two candidates are different.

In the past, Trump has said he would turn management of his companies over to his children and suggested he might consider the idea of a blind trust if he became president.

“If I become president, I couldn’t care less about my company,” Trump said during a presidential debate in Charleston, S.C., in January. “I have Ivanka, and Eric and Don sitting there. Run the company kids, have a good time. I’m going to do it for America.”

His son Eric said in an interview Wednesday that he and his siblings “are handling the business as he runs for president.”

As for Scotland, Eric Trump said, “he is making this trip as much for me as anything,” adding that he and his father have long shared the dream of developing their two golf resorts in Scotland, including Turnberry, which is celebrating its grand reopening after $290 million in renovations overseen by the Trumps.

Reports filed with British authorities show that Turnberry and another Trump course near ­Aberdeen have lost millions of dollars. But Eric Trump said both are on track to become profitable international golf destinations.

“He is in­cred­ibly proud of what we accomplished,” the younger Trump said, explaining the motivation for his father’s visit here.

Donald Trump’s appearance at Turnberry on Friday morning is described as a business event — although it is also listed on Trump’s campaign website. A British communications firm appears to be taking the lead in organizing press coverage, although a media advisory circulated this week also included contact information for a campaign staffer.

Trump previously melded the political and the personal at a press conference in March in the unfinished lobby of the Old Post Office Building on Pennsylvania Avenue in Washington, which he is converting into a hotel that he hopes to open later this year. Standing in front of employees wearing suits, hard hats or chefs jackets, Trump pitched his plans for the “super luxury” hotel — and then took political questions followed by a tour of the construction zone.

And earlier this month, Vanity Fair reported that Trump is considering creating his own media business in order to capi­tal­ize on the following he has drawn as a presidential candidate.

Gross and Painter suggested that Trump should consider using a blind trust as Romney did with many of his assets from Bain Capital. Both expressed some skepticism of the independence of such trusts, as Trump did himself when asked about it during the South Carolina debate.

“I don’t know if it’s a blind trust if Ivanka, Don and Eric run it,” Trump said during the debate, reiterating that his kids would be operating the far-flung business enterprise if he is elected. “I wouldn’t ever be involved because I wouldn’t care about anything but our country, anything,” he said.

Trevor Potter, the election-law lawyer who advised Republican Sen. John McCain on his 2008 presidential bid, called Trump’s efforts “to use the campaign to promote his personal businesses” unprecedented.

But, he said, there is no legal requirement that Trump sever ties to his business empire. The ethics laws that prevent other executive-branch officials from maintaining ties to companies that could benefit from their official actions does not apply to the president or the vice president.

So, are Trump’s ongoing efforts to promote his business a problem?

“That’s a question for the American people — but it is not a legal problem,” Potter said. “The question for the public is: Is this unseemly? Is this something we want our presidents to do — promote their personal businesses around the world?”

Hamburger reported from Washington. Alice Crites in Washington contributed to this report.