The contentious hearing Wednesday before the Senate Judiciary Committee was on the findings of special counsel Robert S. Mueller III, but his voice was absent — as it has been for the last two years.

Attorney General William P. Barr became the latest Trump ally to take advantage of that void, and of Mueller’s constrained conception of his role, by speaking to his description of the work of the special counsel and his interpretation of the Mueller report’s conclusions — all to the advantage of the president. Barr pursued that role so aggressively Wednesday that at times he came across as much a defense lawyer for the president as attorney general of the United States.

In particular, the attorney general downplayed or dismissed the evidence assembled by Mueller that Trump could be guilty of obstructing justice. And he emphasized that Mueller found no proof of collusion between Russia and Trump or his associates.

At times, Barr even took pointed jabs at the former FBI director he has described as a friend, saying Mueller has been sensitive to media criticism and came across as “snitty” in a tersely worded memo the special counsel sent Barr about how the attorney general had summarized his report.

Trump himself sought to preempt the Senate hearing on the Mueller report, tweeting Wednesday morning a conclusion that Barr has repeatedly endorsed: “NO COLLUSION, NO OBSTRUCTION.” Trump’s tweet also called the investigation “the greatest con-job in the history of American Politics!”

Mueller’s reverence for the rule of law and rigid adherence to protocol have bolstered the credibility of the Russia report, which was released with redactions to the public last month. But the special counsel’s deference to procedure and bureaucratic authority has also enabled Trump and his allies to dominate the debate over the investigation’s results.

The disclosure on Tuesday that Mueller had written a private letter to Barr objecting to the attorney general’s characterizations of the report on Russian interference in the 2016 election only underscored the disparity in tactics.

The March 27 letter expressed dismay that Barr’s public description of the report had failed to “fully capture the context, nature, and substance of this office’s work and conclusions.”

But by the time Mueller submitted that memo, Barr’s version of the report’s core findings — including that investigators did not establish a conspiracy with Russia and declined to reach a conclusion on obstruction — had dominated news coverage and established a narrative favorable to the president. It took another five weeks for Mueller’s memo to be revealed to the public.

On Wednesday, even Mueller’s letter of protest was itself being reinterpreted by Barr.

“My understanding was his concern was not the accuracy of the statement of the findings in my letter, but that he wanted more out there to provide additional context,” Barr said. “My view of events was that there was a lot of criticism of the special counsel for the ensuing few days, and on Thursday, I got this letter.”

If Barr recognized the irony of the situation — that he was, once again, characterizing the thinking and position of the special counsel while Mueller remained dutifully silent — he did not acknowledge it.

The sequence was an extension of a pattern established throughout the 22-month probe: Mueller methodically but mutely pursued lines of inquiry, while Trump publicly blasted the special counsel’s team, aiming to discredit its work and convince at least some voters that the inquiry amounted to a partisan conspiracy against his presidency.

The tactic is one that Trump has relied on more broadly in his political ascent — defying norms and conventions that constrain rivals, targeting adversaries with attacks and accusations that they are not prepared or permitted to contest.

Notoriously averse to publicity, Mueller rarely granted interviews during his decade-long tenure as FBI director and resisted being drawn into the kinds of partisan skirmishes that consumed his successor, James B. Comey, when he went public with the bureau’s findings on the Hillary Clinton email investigation.

That reputation for rectitude was largely responsible for the bipartisan support that greeted Mueller’s appointment as the special counsel in 2017. But as he settled into the job, he seemed even more determined to remain out of public view.

Mueller never responded to Trump’s taunts or insults. And the only time he surfaced to address an account in the press was to challenge a BuzzFeed story that was unfavorable to the president.

Even though Mueller and his team rarely engaged with the media, some close to him said he received regular briefings on articles about the investigation. The arrangement suggests that Mueller’s nearly nonexistent public profile was a strategic move to ensure that his team was perceived as impartial.

If the objective was to ensure that the investigation’s findings were embraced by the public, Mueller’s approach by some measures appears to have backfired.

The report and previous indictments include extensive evidence that Russia waged a multiyear “active measures” campaign to disrupt the 2016 race. But recent polls indicate that a majority of Republican voters not only doubt the evidence but don’t believe Russia even attempted to interfere — a view consistent with Trump’s claims that the matter is a hoax.

At one point, Barr likened the special counsel to a prosecutor who had lost a case but wanted credit for his courtroom work. “I’m out there saying here is the verdict, and the prosecutor comes up and taps me on the shoulder and says, ‘Well, the verdict doesn’t really fully capture all my work. How about that great, you know, cross-examination I did?”

Matt Zapotosky contributed to this report.