Confirmation hearings for President Trump's Cabinet nominees are vaulting some Democratic senators into the spotlight.

Lawmakers used their time on the dais to tangle with the picks, sending a clear signal on how they plan to challenge his administration.

The rhetorical war come as Democrats are locked in a post-election fight over who will lead the party and become the face of the opposition to Trump heading into the 2020 presidential race.

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Here are seven Democrats who grabbed headlines in the hearings:

Sen. Cory Booker (N.J.):

Booker scored national attention during Sen. Jeff Sessions Jefferson (Jeff) Beauregard SessionsTrump's policies on refugees are as simple as ABCs Ocasio-Cortez, Velázquez call for convention to decide Puerto Rico status White House officials voted by show of hands on 2018 family separations: report MORE's (R-Ala.) confirmation hearing for attorney general.

The New Jersey Democrat, who typically avoids reporters on Capitol Hill, made history by becoming the first sitting senator to testify against a colleague.

Booker — whose youth, ambition and skilled oratory have drawn comparisons to former President Barack Obama Barack Hussein ObamaThe Hill's 12:30 Report - Presented by Facebook - Don't expect a government check anytime soon Trump appointees stymie recommendations to boost minority voting: report Obama's first presidential memoir, 'A Promised Land,' set for November release MORE — offered scorching testimony against Sessions, saying he wouldn't pursue "civil rights, equal rights and justice for all of our citizens."

Playing off of a quote from Martin Luther King Jr., he added that the "the arc of the universe does not naturally curve toward justice.”

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“America needs an attorney general who is resolute and determined to bend the arc,” Booker said.

Though Booker recently downplayed his presidential ambitions, the potential White House implications of Booker's speech weren't lost on Sen. Tom Cotton Tom Bryant CottonLoeffler calls for hearing in wake of Netflix's 'Cuties' Health care in the crosshairs with new Trump Supreme Court list Cruz says he wouldn't accept Supreme Court nomination MORE (R-Ark.).

"I'm very disappointed that Senator Booker has chosen to start his 2020 presidential campaign by testifying against Senator Sessions,” Cotton wrote in a Facebook post.

Sen. Al Franken Alan (Al) Stuart FrankenPeterson faces fight of his career in deep-red Minnesota district Getting tight — the psychology of cancel culture Tina Smith wins Democratic Senate primary in Minnesota MORE (Minn.):

The former “Saturday Night Live” comedian made noise at several hearings with his sharp questioning.

Franken grilled Sessions on Trump’s rhetoric regarding Muslims and immigrants. He also questioned Trump’s other Cabinet picks over climate change and ObamaCare repeal.

But Franken’s most notable exchange came when he tripped up Betsy DeVos — Trump’s pick for Education secretary — over the contentious debate within education policy circles about whether students’ test scores and success should be measured by proficiency or growth.

DeVos delivered a shaky answer, and Franken cut in to correct her: “It surprises me you don’t know this issue.”

Franken is becoming a top Senate antagonist to Trump’s administration and emerging as a leader within the fractured Democratic Party.

Sen. Kamala Harris (Calif.):

Harris grilled Homeland Security Secretary John Kelly during his hearing, standing out in what was otherwise, in the words of Sen. Heidi Heitkamp Mary (Heidi) Kathryn HeitkampCentrists, progressives rally around Harris pick for VP 70 former senators propose bipartisan caucus for incumbents Susan Collins set to play pivotal role in impeachment drama MORE (D-N.D.), a bipartisan “love fest.”

Harris — the first Indian-American and second black woman in history to hold a Senate seat — pressed Kelly on how the department will handle undocumented immigrants under the Deferred Action for Childhood Arrivals program.

She tried to get the former general to commit to not using personal information provided to the government through the program to deport them and repeatedly tried to get Kelly to commit to not prioritizing their deportation. Harris also managed to get Kelly to acknowledge that he hadn’t talked with Trump about the president’s immigration plans.

Harris separately tangled with Rep. Mick Mulvaney (R-S.C.) — Trump’s pick to lead the Office of Management and Budget — over disaster aid for California, noting that he demanded budget cuts in exchange for federal aid for Hurricane Sandy relief.

The former California attorney general, who is well-connected and already the subject of 2020 speculation, took to Twitter to tout an article about her face-off with Trump’s budget nominee.

Sen. Chris Murphy Christopher (Chris) Scott MurphyDemocratic senator calls for 'more flexible' medical supply chain to counter pandemics The Hill's 12:30 Report - Presented by Facebook - Don't expect a government check anytime soon GOP chairman to release interim report on Biden probe 'in about a week' MORE (Conn.):

Murphy, a vocal advocate of gun control and potential 2020 contender, used his time to ask about an issue close to him: guns in classrooms.

The Connecticut Democrat asked DeVos at her hearing if she believes guns should be allowed in schools. DeVos answered that she would leave the issue to localities and states.

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Murphy continued to press her, "You can't say definitively today that guns shouldn't be in schools?"

DeVos eventually offered a caveat that schools in rural areas might want to have a gun on the premises to protect against "potential grizzlies."

Murphy then questioned whether DeVos would support Trump’s proposal to ban gun-free zones in schools. She noted that she would back whatever actions the president takes, though she noted that her “heart bleeds” for families who have lost loved ones to gun violence.

Murphy appeared teary-eyed after her response and encouraged her to visit his home state, where 20 children and six adults were killed during the 2012 Sandy Hook Elementary School shooting in Newtown, Conn.

Last summer, Murphy held a 15-hour filibuster calling for gun reform.

Sen. Michael Bennet Michael Farrand BennetOVERNIGHT ENERGY: House Democrats tee up vote on climate-focused energy bill next week | EPA reappoints controversial leader to air quality advisory committee | Coronavirus creates delay in Pentagon research for alternative to 'forever chemicals' Senate Democrats demand White House fire controversial head of public lands agency Next crisis, keep people working and give them raises MORE (Colo.):

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The typically mild-mannered Colorado Democrat kicked off his time on the dais on a light-hearted note, thanking Rep. Tom Price (R-Ga.) — a physician and Trump’s pick to lead the Department of Health and Human Services — for examining his knee.

But Bennet’s praise quickly turned into an impassioned monologue about ObamaCare and the potential that a repeal would contribute to the United States' debt and deficit.

Bennet pressed Price on whether he supports a budget that would increase the federal debt by $10 trillion. Price said he supports using the budget reconciliation process, which would enable Senate Republicans to pass the change without crossing the usual 60-vote threshold, as the vehicle to repeal the law.

Reframing the question, Bennet asked if Price could commit to an ObamaCare replacement that would not contribute to America’s deficit or debt. Price said he would “commit” to working with Bennet to ensure this.

“Can’t you tell the Tea Party you’re not going to increase the deficit by repealing the Affordable Care Act?” Bennet asked.

Sen. Bernie Sanders Bernie SandersMcConnell accuses Democrats of sowing division by 'downplaying progress' on election security The Hill's Campaign Report: Arizona shifts towards Biden | Biden prepares for drive-in town hall | New Biden ad targets Latino voters Why Democrats must confront extreme left wing incitement to violence MORE (I-Vt.):

The Vermont senator, who made campaign finance reform a centerpiece of his Democratic presidential primary campaign, drew headlines for asking how much DeVos's family has donated to the Republican Party.

When she couldn't offer a hard number, Sanders asked if an estimate of $20 million was fair, which she conceded was possible.

Sanders separately summoned reporters and TV cameras ahead of the meeting with Price to lay down his own goal posts. Sanders warned that he believed the Georgia lawmaker could move healthcare in the “wrong direction” and urged Trump to support his forthcoming bill allowing Medicare to negotiate drug prices.

Sanders grabbed the spotlight at Price’s hearing, digging in on whether the Trump administration believed healthcare was a “right” for all Americans.

When Price began his response by saying America is a “compassionate society,” Sanders interrupted him.

“We are not a compassionate society,” Sanders fired back.

Sen. Elizabeth Warren Elizabeth WarrenWarren, Schumer introduce plan for next president to cancel ,000 in student debt The Hill's 12:30 Report - Presented by Facebook - Don't expect a government check anytime soon No new taxes for the ultra rich — fix bad tax policy instead MORE (Mass.):

Warren, a potential 2020 contender, had a feisty exchange with DeVos. The liberal favorite repeatedly pressed Trump’s Education pick into admitting that she did not have personal experience with the federal student loan programs that she will oversee and highlighted the $25 million settlement from the now-defunct Trump University.

When DeVos demurred from committing to enforce a gainful employment rule targeted at for-profit colleges — saying instead only that she would review it — Warren interrupted her, noting they had talked about the regulation during a closed-door meeting.

“If you cannot commit to use the tools that are already available to you in the Department of Education, then I don't see how you could be the secretary of Education,” Warren fired back.

Warren took shots at Trump and Trump University, saying that the president had set up a “fake university.” Warren also knocked Senate Republicans for allowing DeVos's hearing to go forward without turning over all of her paperwork.

“I also understand that the precedent was that President Obama's nominees [who] came before committee had all filled out their ethics forms,” she said. “And that those were available before we had a hearing. … So I'm a little confused about what precedent means here.”