The Mueller report — and Mr. McGahn in private testimony before the House Judiciary Committee this month — described Mr. Trump’s anger at Mr. McGahn after the Times article, including trying to persuade him to make a statement falsely denying it. Mr. Trump told aides that Mr. McGahn was a “liar” and a “leaker,” according to former Trump administration officials. In his testimony, Mr. McGahn said that he had been a source for The Post’s follow-up to clarify a nuance — to whom he had conveyed his intentions to resign — but he had not been a source for the original Times article.

There are reasons to doubt that Mr. McGahn was the target of any Justice Department leak investigation stemming from that episode, however. Among others, information about Mr. Trump’s orders to have Mr. Mueller removed does not appear to be the sort of classified national-security secret that can be a crime to disclose without authorization.

Yet another roughly concurrent event is that the subpoena to Apple that swept up Mr. McGahn’s information came shortly after another that the Justice Department had sent to Apple on Feb. 6, 2018, for a leak investigation related to unauthorized disclosures of information about the Russia inquiry, ensnaring data on congressional staff members, their families and at least two members of Congress.

Among those whose data was secretly seized under a gag order, and who were only recently notified, were two Democrats on the House Intelligence Committee: Representatives Eric Swalwell and Adam B. Schiff, both of California. Mr. Schiff, a sharp political adversary of Mr. Trump, is now the panel’s chairman. The Times first reported on that subpoena last week.

Many questions remain unanswered about the events leading up to the subpoenas, including how high they were authorized in the Trump Justice Department and whether investigators anticipated or hoped that they were going to sweep in data on the politically prominent lawmakers. The subpoena sought data on 109 email addresses and phone numbers.

In that case, the leak investigation appeared to have been primarily focused on Michael Bahar, then a staff member on the House Intelligence Committee. People close to Mr. Sessions and Mr. Rosenstein, the top two Justice Department officials at the time, have said that neither knew that prosecutors had sought data about the accounts of lawmakers for that investigation.

It remains unclear whether agents were pursuing a theory that Mr. Bahar had leaked on his own or whether they suspected him of talking to reporters with the approval of lawmakers. Either way, it appears they were unable to prove their suspicions that he was the source of any unauthorized disclosures; the case has been closed, and no charges were brought.