To impeach or not to impeach—it’s the biggest question being asked in Washington, D.C., right now. But it’s not the most urgent. That distinction goes to: Will Robert Mueller testify before Congress? He insisted on May 29, when he made his first and only public statement since being hired as special counsel two years ago, that he would prefer to skip this exercise. That’s unacceptable.

Mueller meant his public statement to snuff out speculation, as well as misrepresentation by Attorney General William Barr and others, about his report. But his carefully chosen sentences have lit fires everywhere—mostly among his detractors who are endeavoring mightily to trash him and his work.

Somewhere Mueller is in “negotiations” with Democrats on the House Judiciary Committee, who are desperately trying to get him to come without a subpoena but will consider using one if he refuses them. Last we heard, in order to avoid the hideous circus of a televised hearing—Rep. Steve Cohen could try and top his toy chicken/fried chicken debacle—Mueller wanted to make an opening statement and then speak privately to members, with an agreement to release the transcript. Translated: He doesn’t want these exchanges to be replayed for all of eternity. Sorry Bob, but sometimes when you investigate history you make it as well. It’s messy.

Especially when the history involves a president like Donald Trump.

Mueller is known for his desire to avoid spectacle and the spotlight, but he has appeared before Congress before, notably after 9/11. Unfortunately for Mueller he is now a central figure in another emergency, and his burden is far heavier than it was in 2001, when others could have informed the public for him.

The president of the United States, the morning after Mueller’s press conference, called his investigators “some of the worst human beings on earth.” Since he likely never read the report, it must have startled him to hear “if we had confidence the president did not commit a crime we would have said so.” Worse, Barr stepped up immediately to muddy up Mueller, summoning a reporter to Alaska to contradict the special counsel—his friend and colleague of three decades—in a brazen television interview that would have been inappropriate for any attorney general to give, ever.

Then, within another day, it became clear a tawdry new whisper campaign was underway about Mueller’s fitness to have conducted the probe, reached his findings, or to talk about them now. I was on the receiving end of some of those whispers myself.

Both Rep. Pete King and Wall Street Journal columnist Peggy Noonan accused Mueller of losing his nerve, but those were the kind assessments. John Solomon of The Hill went on Sean Hannity’s radio show and said:

“some people have looked at that press conference who are linguistics experts have told me it didn’t look like Bob Mueller was reading his own words. He seemed to be unfamiliar. He stumbled or tripped over some of the words. It’s almost like he was reading somebody’s else’s script…. and I’m beginning to hear from defense attorneys, I’m beginning to hear from intelligence professions, that there are things in the Mueller report that don’t jive with the public evidence that they are aware of the private evidence that they have access to.”

Jonathan Turley, writing in The Hill, agrees Mueller must testify but suggests Mueller’s actions and statements are political and complained that: “It was an effort to allude to possible crimes without, in fairness to the accused, clearly and specifically stating those crimes. Mueller knew that was incrimination by omission.”

And not to be outdone, Rudy Giuliani accused Mueller of a “dereliction of duty” in failing to reach a conclusion on obstruction, and threatened on Fox News to bring a qui tam action to get the cost of the investigation back to the Treasury. “What a joke. I think Mueller has made a complete fool out of himself,” Rudy said. Yes, Rudy said that about Bob Mueller.

We know by now Mueller doesn’t respond personal attacks, but his insistence that “the report is my testimony” won’t cut it. There are numerous questions that extend well beyond his findings he must answer. To begin, there are differing accounts about what Barr and Mueller discussed at a meeting on March 5 when Barr insists Mueller told him his decision not to reach a conclusion on obstruction was not because of the guidelines from the Office of Legal Counsel that preclude an indictment of a sitting president. Mueller, citing the OLC guidelines, said the opposite in his statement to the press, that he was bound by them throughout his probe. In testimony he should answer for why, if he knew he would never charge the president with any criminal conduct, he didn’t tell the country that from the start.

Alternately, it’s a good guess from the way Barr speaks these days, that a conclusion by Mueller of criminal conduct by President Trump may have prompted a crisis with Barr likely blasting Mueller for defying the OLC guidelines. Now Mueller is damned for being too cautious. Did Mueller expect Barr and deputy AG Rod Rosenstein to reach a conclusion for him?

Barr has not only contradicted Mueller but himself. In his testimony before Congress on May 1 he said: “We accepted the Special Counsel’s legal framework for purposes of our analysis…in reaching our conclusion.” Yet in his interview with CBS he describes why he overruled Mueller. “We didn’t agree with … a lot of the legal analysis in the report. … So we applied what we thought was the right law,” Barr said, clearly assuming a day after Mueller’s final word that he would have the last word, again, so to speak. What is Mueller’s view?

In testimony Mueller will have to answer questions from Republicans who will focus on Peter Strozk and Lisa Page and James Comey and the Steele dossier and the FISA warrant for Carter Page. Mueller can handle Rep. Jim Jordan. He should prove him right or prove him wrong, but let’s be done with it. There are people counting on Mueller to address many aspects of his findings, but primarily to defend its legitimacy to the public in detail. When I asked Democratic Senator Mark Warner, at a Christian Science Monitor breakfast May 9, why he has said his committee intends to tell a fuller story of the extent of Russia’s attack than the Mueller report did, he answered—somewhat cryptically—that he has many questions for Mueller about his process as well as his findings: “Why didn’t Mueller finish? There’s great controversy around the Steele Dossier and I mean I think it was glancingly mentioned at best and I’d like to know—they had a lot more resources than we, I think that’s an important issue for the American people.”

Warner also made clear, when asked about investigating the investigators, that the people attacking the probe haven’t seen the underlying evidence, and those who have seen it—like the Republicans he serves on the Senate Intelligence Committee with—aren’t calling for it, or criticizing Mueller’s team or work.

The special counsel must also speak to Barr’s refusal, on CBS, to defend Mueller’s team, or the legitimacy of the probe. When asked if the special counsel investigators committed treason, Barr quipped, “not in the legal sense.” His loyalty and priority, he made clear, are certainly not the preservation and protection of the Department of Justice’s integrity.

Barr said when he has asked questions of investigators the answers he has received aren’t satisfactory and that some of the “facts don’t hang together.” When asked to clarify he refused. “That’s all I really will say. Things are just not jiving.” He declined numerous times to provide evidence of dubious conduct by any investigators. This is the sort of aspersion-casting-without-bringing-charges Trump allies accused first Comey, then last week Mueller, of doing. Only this is worse, as Barr is denigrating law enforcement officials in his department.

Barr has also joined Giuliani, Trump, and Jared Kushner in inviting foreign interference in next year’s election by talking about everything but this threat. Mueller, who took pains to open and close his statement last week stating a “concerted attack” by the Russians should concern every American, knows he should give more voice to the urgency of this threat, because people haven’t read his report. The average voter has no idea that FBI Director Chris Wray and Director of National Intelligence Dan Coats have said the same thing.

Multiple lawmakers and commentators have said that simply having Mueller re-stating some of his findings on camera would break through since, well, Americans are lazy and uninterested in reading the 448-page report so they won’t know how damning it is until someone reads it to them on cable television. That would be a dereliction of duty for Democrats, as these other questions speak to the credibility of the DoJ, FBI, and the sanctity of the rule of law.

Mueller is the only person who can answer them. Not Comey, Andrew McCabe or Jim Baker, and definitely not Barr. Before Barr books another television interview, Mueller—the old Marine—needs to make one more sacrifice for his country.