Maybe not the only one running it, the Times suggests, but Bob Mueller doesn’t seem to have been a core part of the leadership team.

“It’s inconceivable that Robert Mueller ran this investigation,” said Andy McCarthy on Fox News this morning after taking in Mueller’s performance yesterday. “One thing that was evident in seven hours of testimony is that he only has a remote familiarity with his own report and with the investigation. He was actually staff-driven and that’s what the president has been saying all along.” Kellyanne Conway echoed the point elsewhere, albeit in a kinder way — sort of:

“I am first and foremost who I will always be, which is a daughter, a mother,” Conway told conservative talk radio host Hugh Hewitt during an interview on his show Thursday morning.

“And, of course, I feel great empathy and compassion for folks who, as some of these headlines suggest, may be feeble or not understanding some of the questions — asking them to be repeated, clearly not conversant with the facts and with his own report,” she continued.

Mueller’s halting testimony made the question of who was really in charge inescapable. The Times provides a probable answer: It was Aaron Zebley, the aide who accompanied him to yesterday’s hearing and was allowed by House Democrats to “advise” him on his answers. For good reason, it seems.

Soon after the special counsel’s office opened in 2017, some aides noticed that Robert S. Mueller III kept noticeably shorter hours than he had as F.B.I. director, when he showed up at the bureau daily at 6 a.m. and often worked nights.

He seemed to cede substantial responsibility to his top deputies, including Aaron Zebley, who managed day-to-day operations and often reported on the investigation’s progress up the chain in the Justice Department. As negotiations with President Trump’s lawyers about interviewing him dragged on, for example, Mr. Mueller took part less and less, according to people familiar with how the office worked…

The calendars of one of the team’s top prosecutors, Andrew Weissmann, suggest that he met infrequently with Mr. Mueller apart from a daily 5 p.m. staff meeting, which typically lasted 45 minutes.

Instead, the calendars cite Mr. Zebley’s initials 111 times, often next to “team leader” meetings, suggesting he may have led them.

Has this ever been reported before anywhere? I’m not one of the Internet’s Russiagate obsessives, familiar with minutiae of the probe, but I followed it as closely as anyone who comments on national news for a living might be expected to. I can’t recall even reading the name “Aaron Zebley” before this week, although doubtless it showed up in Mueller stories in passing. I know I’d remember seeing it if any mainstream news source had suggested that Mueller wasn’t fit for command and was serving in a largely figurehead role while his deputies, led by Zebley, handled the business of the investigation. That would have been a bombshell, throwing the probe’s credibility into doubt; Trump surely would have amplified it too in his daily rants about the investigation. “Daffy old Bob Mueller can’t find his way home! How can he find the truth about my innocence?”

Remember, Zebley previously represented the IT aide who set up Hillary Clinton’s email server. If it had been previously reported that he was the de facto head of the probe, you think POTUS might have noticed? Instead, not a peep.

And so: Are we to believe that American media knew nothing about Mueller’s … situation for two years until yesterday, when House Democrats inadvertently forced him to reveal his unfamiliarity with some of the basics of the case? Or did they have reason to believe that Mueller was unfit and/or not actually leading the probe but kept that fact quiet for their own ideological reasons, knowing how Trump would exploit it if he knew? Politico noted yesterday afternoon that “House Democrats caught wind of Robert Mueller’s reluctance earlier this year: the special counsel may not be ‘up to’ testifying after he concluded his Russia probe,” calling the chatter “second-hand and cryptic.” If House Dems were hearing it, reporters were surely hearing it too.

Did they try to chase it down? The news value of that scoop obviously would have been momentous.

I won’t fault anyone who chooses to believe that they knew and looked the other way to protect Mueller and the left’s chances of taking down Trump. But I can also see how it would have been hard to nail down a “Bob Mueller’s not up to leading the Mueller probe” story. For starters, Team Mueller was famous for not leaking about the investigation. Imagine how much more reluctant they would have been to leak about the “condition” of Bob Mueller, a man whom they admired and whose unfitness might have jeopardized the entire probe had it been public knowledge. For all Mueller’s deputies knew, Trump might have seized on news of Mueller’s frailty as a pretext to fire him and try to end the investigation, risking a constitutional crisis. They may have kept this as their most closely guarded secret, with no one breathing a word to the media. The fact that Mueller refused to do interviews, believing that a prosecutor should speak only through his indictments, made that option tenable.

Also, without an official diagnosis from a doctor, how could a news outlet feel confident enough about a claim that Mueller had grown frail to print it on page one? It’s unlikely that aides and friends would say bluntly that they feared he’d become “feeble” or senile. More likely they’d dance around it, allowing that he’d “lost a step,” which means … what, precisely? Mueller is still sharp enough to have (barely) gotten through two House hearings yesterday. So if you’re a New York Times reporter and you have a couple of people telling you he might not be “up to” running the probe but you also inevitably have other people insisting that he’s fine, just fine, never better, what do you do with that information? Do you run it, knowing that you’d be throwing a match into a political powder keg based on a couple of people’s unscientific perceptions, or do you wait and sniff around for stronger evidence?

Look at it this way: If the media had heard about Mueller’s condition, chances are high that Washington Republicans were hearing about it through the grapevine too. Yet I don’t recall any GOPers, starting with Trump, ever attacking Mueller along these lines — and the Trump-era GOP isn’t know for fighting by Queensbury rules. They would have used if they had had it. So maybe they didn’t have it. And if they didn’t, maybe reporters didn’t either.

Exit question: If Mueller’s condition was commonly known in D.C., would House Dems really have allowed him to testify yesterday? Or would they have manufactured some excuse and asked Zebley to testify instead? Come to think of it, will Zebley testify now? Or has the public’s attention span for all things Russiagate finally been extinguished?