“You used the president’s words — obstruction — over and over again,” Mr. Booker told Mr. Barr. He was into the next question by the time he caught himself: “I’m sorry — ‘collusion’ is the word I was looking for. You used the word ‘no collusion’ over and over again.”

Outside Washington, Democrats on the campaign trail were also seizing on the hearing for political gain, with several — including Senators Kirsten Gillibrand and Elizabeth Warren; the former housing secretary Julián Castro; and Mr. Biden — also calling for Mr. Barr’s resignation.

“I think he’s lost the confidence of the American people,” Mr. Biden told reporters in Iowa.

Democrats, of course, were not the only ones posturing. Mr. Graham opened the hearing by brandishing a printed copy of the 448-page Mueller report, holding it in the air as dozens of camera shutters clicked. He used his remarks to once again train a spotlight on Mr. Trump’s 2016 Democratic opponent, Hillary Clinton, and the anti-Trump texts of the former F.B.I. agents who investigated the Trump campaign.

“What do we know?” Mr. Graham asked acidly. “We know that the person in charge of investigating hated Trump’s guts.”

Congressional committee hearings are always part substance and part political theater, and in the theatrics department, the Kavanaugh hearings produced more memorable moments.

Ms. Klobuchar emerged a clear winner then; when she disclosed her father’s battle with alcoholism, then-Judge Kavanaugh lashed out at her — and subsequently offered an apology, which elevated the senator’s national profile while she was still contemplating a White House run. Ms. Harris employed her same style of rat-a-tat questioning, but it seemed to lead to nowhere.

But none of that compared with Mr. Booker’s threat to release emails with the declaration, “This is about the closest I’ll ever come in my life to an ‘I am Spartacus’ moment.” His comments were roundly mocked by conservatives, including The Washington Post columnist Kathleen Parker (“Gambling everything, he won a punch line,” she wrote) and Justice Clarence Thomas.

On Wednesday, Ms. Harris seemed to come out on top, judging by the coverage on Fox News, which gave her top billing. “Kamala Harris tears into Barr at Senate hearing, as 2020 Dems pile on AG,” the headline on its website blared.