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Donald Trump’s inauguration is still a week away, but opposing the president-elect is good politics for any ambitious Democrat with eyes on a White House bid.

That could be why some of the most outspoken opposition to Trump’s cabinet appointees during this week’s confirmation hearings has come from Democrats widely seen as potential presidential contenders four years from now. For the next four years, those politicians will be in competition with each other for the hearts, minds and dollars of angry liberals eager for anti-Trump champions.

New Jersey Sen. Cory Booker was the most brazen in using the confirmation hearings to raise his personal profile, breaking precedent to become the first senator in history testify against a fellow member of the chamber. He was swarmed by reporters as he left the hearing room where he spoke out against Alabama Sen. Jeff Sessions, Trump’s pick for Attorney General.

But other up-and-coming senators often mentioned in Democrats' 2020 fantasy draft picks leveraged the spotlight on their committees’ hearings to press their issues and demonstrate their rhetorical chops.

Massachusetts Sen. Elizabeth Warren has a knack for creating viral moments out of dreary hearings, and she used it to make Dr. Ben Carson squirm Thursday as she tried to get him to promise that none of the billions of dollars distributed by the Department of Housing and Urban Development, the agency he’s been tapped to lead, would benefit Trump or his real estate empire.

Carson refused to give a yes or no answer, and got tongue-tied as he evaded the question.

"It will not be my intention to do anything that will benefit any American," Carson said, misspeaking.

“The reason you can't assure us of that is because the president-elect is hiding his family's business interests from you, from me, from the rest of America," Warren responded.

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Ohio Sen. Sherrod Brown, who has been floated as a Rust-Belt savior for Democrats, also got a chance to put Carson in the hotseat when he pressed the nominee on his views on the minimum wage, another topic where Carson wiggled out of a definitive answer.

Meanwhile, just days into her much-anticipated Senate career, California Sen. Kamala Harris interrupted what was otherwise a bipartisan “lovefest” — as another Democratic member of the committee described it — with the only adversarial line of questioning directed at Trump's pick for Secretary of Homeland Security, John Kelly.

She pressed the retired Marine general on whether undocumented immigrants granted special status by the Obama administration would have information they provided to the government used against them.

“I’m not familiar right now where the upcoming administration is going,” Kelly acknowledged.

Democrats on the Judiciary Committee, which must approve Sessions, largely held their fire on their colleague — except for Minnesota Sen. Al Franken, who earned laudatory headlines from progressive news outlets for grilling his fellow senator on alleged exaggerations his civil rights record.

It was one of several notable exchanges Franken had with Sessions, displaying the acerbic wit that has propelled his rise from successful comedian to the U.S. Senate.

Over at the Senate Foreign Relations Committee, Sen. Chris Murphy demonstrated why he has become one of his party’s most prominent new voices on foreign policy. Secretary of State nominee Rex Tillerson took on water during tough questioning on Russia from a number of senators from both parties.

But the 43-year-old Murphy stood out by moving beyond Russia. He created a cringe-inducing moment for Tillerson when the former ExxonMobil CEO repeatedly refused Murphy's invitation to condemn human rights violations in countries where he had done business

Tillerson even gave a pass to Philippines President Rodrigo Duterte, who has bragged about extrajudicial killings of drug dealers in his country.

“I’m not going to act on what people write about in the newspapers or even what people may brag they’ve done. Because people brag about things that they may or may not have done,” Tillerson said.

But Booker’s decision to break the Senate's unwritten rules on collegiality towards fellow members ensured there would be plenty of people watching on a very crowded news day, when he gave his testimony against Sessions Wednesday.

Booker, the Senate's only black Democrat until Harris' arrival, showed off his oratory power by riffing on Martin Luther King Jr.’s maxim that the arc of the moral universe bends towards justice.

“America needs an Attorney General who is resolute and determined to bend the arc,” Booker said. “Senator Sessions’ record does not speak to that desire, intention, or will,” Booker said.

He was backed up in the room by members of the Congressional Black Caucus and Rep. John Lewis, the civil rights icon. In his own testimony, Lewis noted that he grew up “not far” from Sessions in Alabama, and still bears the scars put there by the state’s troopers billy clubs on the Edmund Pettis Bridge in Selma.

Republicans dismissed Booker’s testimony as a political stunt, and nine of the the Judiciary Committee's 11 Republican members stayed out of the room while Booker spoke.

Arkansas Republican Sen. Tom Cotton wrote on Facebook that Booker’s “disgraceful breach of custom” was nothing but “a platform for his presidential aspirations.” Sen. Ted Cruz, who knows a thing or two about running for president as a freshman senator, told a talk radio show host, “It's not lost on anyone that Cory is ambitious.”

But the controversy only heightened interest in Booker’s message.

Khizr Khan, the Gold Star father who spoke out against Trump during the campaign, told NBC News he appreciated Booker for putting his ideals over the Senate's clubby norms. Khan wrote a letter calling the Judiciary Committee to nix Sessions, and came to support opponents' efforts, but he wasn't hopeful.

"I have no illusions that he won't be confirmed," Khan said.