Yet the Times expressed doubt about that denial. “According to the others who described his comments, Mr. Rosenstein not only confirmed that he was serious about the idea but also followed up by suggesting that other F.B.I. officials who were interviewing to be the bureau’s director could also secretly record Mr. Trump,” the paper said.

It’s difficult, at this stage, to assess the story and what really happened on its own terms. The primary source for the Times report appears to be a tranche of memos written by McCabe, who was fired earlier this year. McCabe was a protégé of James Comey, whose own memos sparked Rosenstein’s appointment of Robert Mueller as special counsel. In addition to the spokeswoman who said Rosenstein was not serious, the Times reporters spoke to people “briefed either on the events themselves or on memos written by F.B.I. officials.”

While the facts remain a bit hazy, there’s another question to consider: Cui bono? In other words, who might stand to benefit from the leak? And does that tell us anything about who might have leaked?

It’s possible that leaking the memos could exculpate McCabe, who was stung by his firing and is suing the government. The leak of Comey’s memos painted him in a positive light, buttressing his accounts and suggesting that Trump was not telling the truth. The former Justice Department spokesman Matthew Miller, who served during the Obama administration, implied that McCabe might be the leaker, but McCabe’s lawyer denied it, even as he effectively confirmed the veracity of the memos, and said that McCabe had shared them with Mueller. If McCabe were the leaker, it’d be a dangerous step for him to take: The memos may or may not help him, but they almost certainly hand his nemesis Trump a powerful weapon. By leaking, McCabe would be cutting off his nose to spite his face.

One possible goal of the leak, as Rosenstein argued in his statement, may have been to hurt him and the Justice Department. The deputy attorney general has been in the hot seat for most of his tenure. After Attorney General Jeff Sessions’ recusal from Russia-related matters, Rosenstein became the point man. It was his decision to appoint Mueller in the aftermath of the Comey firing, and that decision enraged Trump. The president has repeatedly called for Mueller’s firing and has called the probe a “witch hunt.” Trump also claimed falsely that he didn’t know anything about Rosenstein (he appointed him) and that he is a Democrat (he is not).

There’s always a new low for the Trump White House.

More recently, Rosenstein and Trump are said to have forged a better rapport, even as Trump’s relationship with Sessions deteriorates (although the president continues to rage against the Mueller probe). This report could torpedo that. Even if the incident happened more than a year ago and Rosenstein was not serious, Trump has been known to fire people for less, and to lose his temper easily.