It did not take long — just 13 words — for Senator Kamala Harris to jump in.
The chairman of the Senate Judiciary Committee had just gaveled the first day of Judge Brett M. Kavanaugh’s confirmation hearings to order and was about to utter his 14th word when Ms. Harris, Democrat of California, interrupted, demanding a delay to give the panel time to review a last-minute document dump.
“We cannot possibly move forward,” she protested, as the chairman, Senator Charles E. Grassley of Iowa, promptly ruled her out of order.
It was a made-for-television moment, and it might come in handy for Ms. Harris. She is one of three Democrats on the judiciary panel — the others are Senators Cory Booker of New Jersey and Amy Klobuchar of Minnesota — said to be contemplating presidential runs in 2020, and there is no time like a stately, nationally televised Supreme Court nomination hearing to grab media attention and amass valuable footage for future campaign commercials.
Other 2020 hopefuls, notably Senators Kirstin Gillibrand of New York and Elizabeth Warren, have been making their own moves this week. Ms. Gillibrand, who has positioned herself as a leading advocate for women’s rights, has been appearing with women’s groups to protest the nomination, calling it “a clear threat to rights that women all across America hold dear.”
And Ms. Warren, notoriously press shy in the corridors of the Capitol, told Politico on Wednesday that she intends to “open up” and start giving hallway interviews.
But for Ms. Harris and Mr. Booker — and to a lesser extent, Ms. Klobuchar, who is less given to high drama — the hearings have been something like a campaign audition.
On Thursday morning, Mr. Booker threatened to release documents marked “committee confidential,” even if it meant being expelled from the Senate. He dramatically declared, “This is about the closest I’ll ever come in my life to an ‘I am Spartacus’ moment” — nevermind that some of those documents had already been released by The New York Times.
Republicans mocked the moment with acid notes on Mr. Booker’s ambitions. “Running for president is no excuse for violating the rules of the Senate or of confidentiality of the documents that we are privy to,” snapped Senator John Cornyn, Republican of Texas.
On Wednesday night, Mr. Booker talked for a full 23 of the 30 minutes he was allotted to question Judge Kavanaugh, delivering a soaring lecture on racial inequality — even as he repeatedly cut off the nominee while grilling him about his views on affirmative action, racial profiling and voter identification laws.
“It seems that you are O.K. with using race to single out some Americans for extra security measures because they look different, but you’re not O.K. with using race to help promote diversity,” Mr. Booker said at one point, while disclosing that the committee has a confidential email titled “racial profiling” relating to Judge Kavanaugh.
Not to be outdone, Ms. Harris, a former California attorney general, drew on her formidable skills as a former prosecutor to repeatedly skewer Judge Kavanaugh and back him into unpleasant corners.
“Can you think of any laws that give the government the power to make decisions about the male body?” she asked at one point, in an exchange that picked up considerable traction on social media.
The judge seemed flustered. “I’m not — I’m not — thinking of any right now, senator,” he replied.
For Mr. Booker and Ms. Harris, both darlings of the progressive movement, the hearings are also a chance to demonstrate fidelity to the left. Progressives have become increasingly frustrated with the way Senate Democrats are handling Judge Kavanaugh’s nomination; on Wednesday, more than a dozen groups sent a scathing letter to Senator Chuck Schumer of New York, the Democratic leader, accusing him of allowing moderate Democrats to go their own way in considering whether to vote for confirmation.
At the same time, the posturing by the 2020 hopefuls has not escaped the notice of Republicans, who are accusing the Democrats of playing politics with one of the most sacred duties of the Senate: the responsibility to advise and consent on a Supreme Court nomination.
Mr. Booker came in for withering criticism on Wednesday when he sent a letter to supporters asking for signatures opposing Judge Kavanaugh. The letter, which circulated on Twitter, asked recipients to click through to a website that offered tickets to an upcoming New Jersey Democratic State Committee event. Republicans blasted Mr. Booker, accusing him of using the hearings to raise money.
As Mr. Cornyn, the No. 2 Republican in the Senate, wrote on Twitter: “It’s all about the 2020 Democrat presidential primary.”