He was one of the very few members of Mr. Trump’s post-presidential office when Mr. Trump first returned to private life at his club, Mar-a-Lago, in Palm Beach, Fla. There, Mr. Nauta resumed the kind of personal chores that he had helped Mr. Trump with while he was president.

Mr. Nauta has been seen as deeply loyal to Mr. Trump by other aides.

But he attracted the attention of the government for his appearance on security camera footage from the club, which was subpoenaed by prosecutors, moving boxes in and out of a basement storage room after a grand jury subpoena.

In interviews with government officials, according to the indictment, he gave false testimony about whether he had moved boxes to Mr. Trump’s residence earlier in the year. In reality, according to the indictment, Mr. Nauta brought several boxes to Mr. Trump’s residence from the storage room at a time when National Archives officials were seeking the return of presidential material, but he told investigators he didn’t.

In another memorable moment noted in the indictment, on Dec. 7, 2021, Mr. Nauta discovered that some of the boxes in the storage room had fallen and their contents were all over the floor, “including a document marked ‘SECRET//REL TO USA, FVEY,’ which denoted that the information in the document was releasable only to the Five Eyes intelligence alliance consisting of Australia, Canada, New Zealand, Britain and the United States.”

Mr. Nauta texted a colleague and wrote, “I opened the door and found this…”

Prosecutors have been weighing charging Mr. Nauta since the fall, but had been pressuring him to cooperate with their investigation. He declined.