“Traditionally, nominees travel overseas during this period to brush up their foreign policy depth and visit 10 Downing Street and Israel — for politics back here,” said Scott W. Reed, senior political strategist for the U.S. Chamber of Commerce. “Everyone knows this is the wrong thing for the nominee to be doing now, and it is amazing this can’t be stopped.”

Mr. Trump will arrive Friday at Trump Turnberry, a luxury golf course and resort dating to the 1900s that he bought in 2014. The property features picturesque views of the Irish Sea and suites costing as much as 800 pounds — roughly $1,200 — a night.

He has told aides that he hopes the trip, which includes a stop in Aberdeen on Saturday, will provide a much-needed reset for his campaign. But some of the aides have said privately that they wished he would cancel it.

Mr. Trump’s self-image as a successful businessman is important to him, and, though he has said publicly that he is relying more on his children to run the Trump Organization, he remains closely tied to it. He also believes that many of his supporters are drawn to his persona of a brash billionaire, born out of his decades in the business world.

He does not like to be away from his business operations for long. Save for a little more than a dozen nights during the primaries, he has returned to one of his homes at the end of each day. He usually returns to his New York City apartment, which allows him access to his 26th-floor office in Trump Tower, where he works and takes part in interviews. And he tends to rely on Trump-connected businesses while he is campaigning, further bringing together the two worlds in which he operates.