Then-special counsel Robert S. Mueller III arrives to make a statement on May 29 at the Justice Department in Washington. (Salwan Georges/The Washington Post)
Contributing columnist

It tells you a lot about what to expect from former special counsel Robert S. Mueller III’s testimony before the House Judiciary and Intelligence committees on July 17 that Mueller agreed to appear in response to a House subpoena even though he apparently would prefer to walk over hot coals.

Mueller is now a private citizen, and even when he was still in the Justice Department as special counsel, Attorney General William P. Barr pledged to leave to Mueller the decision of whether he would testify. Mueller’s “decision,” announced at the end of his 10-minute appearance on May 29, was that he did not want to testify and that, if called, he would stick to the four corners of the report.

In the event, however, Congress lodged a legal demand, and the former Marine answered the call, while making clear to Congress that he was not happy about it. It was completely open to him to resist the subpoena with the sort of bad-faith, even ludicrous legal argument that is now the reflexive strategy of the White House and the Justice Department. But Mueller has too much integrity and respect for the law to resort to such disingenuous shenanigans.

So he will come, and on July 17 — assuming, that is, that Barr remains hands off. But which questions will he answer, and which will he attempt to parry?

The widespread expectation, conditioned by Mueller himself, is that he will stick to the written text of the report, perhaps even giving “see page 85”-type responses that would deny the committees the dramatic TV moments they have been increasingly desperate to choreograph.

Even so, his testimony could be seismic. After all, his May 29 statement was crafted to be bland and factual, but hearing it from the laconic Mueller had an electrifying effect. Moreover, if the testimony does no more than illuminate the report’s factual account, it nevertheless has the potential to be something of a game-changer.

That’s because the bare facts laid out in the report plainly chronicle 1) appalling misconduct by the Trump campaign in consorting with Russia and 2) unmistakable instances — at least four — of obstruction of justice. But after Barr got out front with his wildly slanted assessment of the evidence, the House committees have made scarcely any headway toward explaining the gravity of the facts the report chronicled (thus the ingenious decision by Annette Bening and other stars earlier this week to read the report in public as if it were a piece of radio theater). Mueller’s public explanation — delivered in his polite but crisp and acutely perceptive manner — can only help bring the dry-but-damning points in the report to life.

But that’s just for starters. Because in fact, the widespread assumption that Mueller will stick to the four corners of the report is, at a minimum, problematic. He is responding to a lawful subpoena by a separate branch of government imbued with oversight power. It is not clear on what basis he could try to draw the line at the paper report. He could point to general Justice policies and practices, but they have been honored in the breach so far in his probe (including producing the report to Congress at all) and don’t in any event provide a clear constitutional justification for refusing to answer lawful questions from Congress.

Take even the $64,000 question: Mr. Mueller, would you have found obstruction if you were not limited by the Justice Department’s Office of Legal Counsel determination that the Constitution forbids indictment of a sitting president? Mueller could object strenuously (though, invariably, with impeccable politeness) and insist the question is irrelevant. But if the committee at that point thanked him for his judgment but insisted he answer the question, Mueller’s legal case for resisting appears thin.

Of course, it likely won’t be a matter of a dry legal analysis. However strong Congress’s legal hand might be, it is extraordinarily unlikely to go to court to vindicate it, which among other stark inconveniences would entail holding Mueller in contempt. Members of Congress also lose politically if they make Mueller angry and recalcitrant. Mueller knows all that, yet he also is too respectful of the law to be ultra-cagey.

That all points to a series of delicate exchanges in which members of the committees press him — but not too hard — for important information outside the text of the report, and Mueller resists — but not too stridently — and eventually gives some ground. Of course the exact ground matters, but the overall result will likely be, by far, the best, most important news for the committees since the issuance of the report itself.

Read more:

Jennifer Rubin: Four reasons Mueller’s agreement to testify is a big deal

Robert S. Litt and Benjamin Wittes: 20 questions Mueller will actually be able to answer

Greg Sargent: How Mueller’s testimony could expose one of Trump’s biggest crimes

Harry Litman: The most important day in the Mueller probe was deeply upsetting

Randall D. Eliason: Was Mueller’s dodge on obstruction a blunder — or brilliant?