(CNN) As the top two vote-getters in Iowa, Pete Buttigieg and Bernie Sanders became the chief targets of their Democratic presidential rivals, who repeatedly challenged them on their experience and electability during a fiery final debate in New Hampshire Friday night before Tuesday's primary.

Though the ABC News moderators breezed through many different topics over the two-and-half-hour face-off, the quarrels over the duo's qualifications for the White House produced the sharpest and most memorable moments of the debate at Saint Anselm College, as all the contenders tried to show they would be the strongest candidate to take on President Donald Trump. Minnesota Sen. Amy Klobuchar and former Vice President Joe Biden pointedly sought to portray 38-year-old Buttigieg as too green for the White House, while Sanders argued that Buttigieg's reliance on big-dollar donors meant that he was buying into a corrupt system and would be beholden to big-money interests.

While much of the heat focused on Buttigieg, a number of the candidates onstage said they believed Sanders' background as a democratic socialist would become an albatross during a difficult race against Trump. Buttigieg took that a step further by rejecting what he views as Sanders' uncompromising and divisive approach to politics.

One of the candidates to score the cleanest hits on Buttigieg was Klobuchar, and donors impressed by her performance splashed out $1 million to her campaign coffers following the debate.

The Minnesota senator suggested that Buttigieg has not taken weighty matters like impeachment seriously enough.

"As you were campaigning through Iowa, as three of us were jurors in that impeachment hearing, you said it was exhausting to watch and that you wanted to turn the channel and watch cartoons," she said.

Klobuchar added, "I don't think that's what people want right now. We have a newcomer in the White House, and look where it got us. I think having some experience is a good thing."

The clashes began within the first few minutes of the debate, when ABC moderators pressed Biden on his recent assertion that Democrats would be taking a big risk by choosing Buttigieg or Sanders.

"With regard to Sen. Sanders, the President wants very much to stick a label on every candidate. We're going to not only have to win this time, we have to bring along the United States Senate," Biden said referring to Democratic hopes of taking control of that body. "Bernie's labeled himself -- not me -- a democratic socialist. I think that's the label that the President's going to lay on everyone running with Bernie, if he's a nominee."

Buttigieg, Biden added, "is a great guy and a real patriot." But he added: "He's a mayor of a small city who has done some good things, but has not demonstrated he has the ability to -- and we'll soon find out -- to get a broad scope of support ... including African Americans and Latinos."

Even businessman Tom Steyer questioned Buttigieg's experience.

JUST WATCHED Why Steyer thinks he has more experience than Buttigieg Replay More Videos ... MUST WATCH Why Steyer thinks he has more experience than Buttigieg 01:28

"The question is, who can go toe to toe with Mr. Trump? Who can take down Mr. Trump? Because he's the real threat to the country," Steyer said. "We need people with experience. That's why I'm worried about Mayor Pete. You need to be able to go toe to toe with this guy and take him down on the debate stage or we're going to lose."

The former South Bend, Indiana, mayor, who would later be forced to defend his record on race, defined his experience as "a different perspective" and one that would allow the Democratic Party to "leave the politics of the past in the past, turn the page and bring change to Washington before it's too late."

"I freely admit that if you're looking for the person with the most years of Washington establishment experience under their belt, you've got your candidate, and of course it's not me," said Buttigieg, who has pointed to his military service in Afghanistan as a key part of his experience.

But Buttigieg's rivals were persistent in questioning whether he was ready for the rigors of the White House. Klobuchar said she could just as easily claim the mantle of being the fresh face on the stage: "Fifty-nine, my age, is the new 38," she quipped.

In her closing statement, the Minnesota senator noted that she was not the biggest name on the stage, nor does she have the biggest bank account. For emphasis, she directed a final zinger in Buttigieg's direction: "I'm not a political newcomer with no record, but I have a record of fighting for people."

Sanders, who had largely ignored Buttigieg on the campaign trail until the former mayor's surprisingly strong finish in Iowa , took up an argument that Massachusetts Sen. Elizabeth Warren has made for several months -- that Buttigieg's big-dollar fundraising success is a corrupting force that should be rejected by voters.

"If we want to change America, you're not going to do it by electing candidates who are going out to rich people's homes begging for money," Sanders said, noting that his average contribution is $18.50.

Buttigieg replied that Democrats are in "the fight of our lives" against Trump. He noted that the Republican President and his allies raised $25 million on Friday, according to news reports.

"We need to go into that fight with everything that we've got," Buttigieg said.

He defended his record by noting that he has sued pharmaceutical companies, and has campaigned on raising wages and raising taxes on corporations, as well as the wealthy.

"As the only person on this stage who is not a millionaire or a billionaire, I know a thing or two about building a movement, because mayor of South Bend, Indiana, is not exactly an establishment fundraising powerhouse," he said. "This is a time for addition, not rejection, for belonging, not exclusion."

Figuring out if a progressive or a centrist can beat Trump

That statement echoed a line that Buttigieg had used earlier in the night to criticize Sanders. Buttigieg described the race against Trump as a new moment in American politics, one that required a new style of leadership that he said he could offer.

"This is a moment where the next president is going to face challenges the likes of which we hadn't even thought of a few years or decades ago. And politically, we're facing a fundamentally new problem with President Donald Trump," Buttigieg said.

He added that "the biggest risk we could take at a time like this" would be for Democrats to choose a nominee who is "dividing people with the politics that says, 'If you don't go all the way to the edge, it doesn't count,' a politics that says 'It's my way or the highway.' "

"Are you talking about Sen. Sanders?" ABC moderator George Stephanopoulos asked.

"Yes," Buttigieg replied. "Because we've got to bring as many people as we can into this process."

Earlier in the night, when Sanders was asked why Democrats shouldn't be worried about the labels that Trump would use against him, he argued that he would be able to bring people together and bring new voters into the process.

"I believe that the way we beat Trump is by having the largest voter turnout in the history of this country," Sanders said. "That is appealing to working-class people who have given up on the political process, because they don't believe anybody is hearing their pain, perceiving that pain, feeling their pain, and we got to bring young people into the political process."

MANCHESTER, NEW HAMPSHIRE - FEBRUARY 07: Sen. Amy Klobuchar (D-MN) participates in the Democratic presidential primary debate in the Sullivan Arena at St. Anselm College on February 07, 2020 in Manchester, New Hampshire. Seven candidates qualified for the second Democratic presidential primary debate of 2020 which comes just days before the New Hampshire primary on February 11. (Photo by Joe Raedle/Getty Images)

But when asked if they were worried about the fate of their party should it be led by a democratic socialist, other Democrats on stage raised their hands.

"Bernie and I work together all the time, but I think we are not going to be able to out-divide the divider in chief," Klobuchar said. "Donald Trump's worst nightmare is a candidate that will bring people in, from the middle, the people that are tired of the noise and the nonsense."

A new poll by NBC News and Marist in New Hampshire, which was conducted after the Iowa caucuses, showed Sanders and Buttigieg battling for first place in New Hampshire with Sanders at 25% and Buttigieg at 21%. Biden and Warren were tied in a distant third place and no one else rose above single digits.

On a night when Warren needed a standout performance to catapult her back into contention with Sanders and Buttigieg, the Massachusetts senator often seemed to recede at key moments.

She spoke most forcefully on race and the gaping disparities in how white people and people of color are treated within the criminal justice system.

That issue became a central focus when one of the ABC moderators questioned Buttigieg about why there was such a striking disparity in arrest rates for black and white residents in his hometown while he was mayor.

ABC moderator Linsey Davis noted that a black resident in South Bend was four times more likely to be arrested for marijuana possession than a white resident. She said that racial disparity was higher there than in the rest of the state and the rest of the nation, and that it had increased in South Bend after he took office.

Buttigieg, who has almost no support from African Americans in national polling, replied that drug arrests in South Bend were lower than the national average. He added "that there is no question that systemic racism has penetrated to every level of our system, and my city was not immune."

Without explaining that aspect of his record in any detail -- other than to say the city had adopted a strategy of cracking down on drug enforcement in cases connected to gangs or violent crime -- the former mayor discussed his more abstract goals for remedying racial injustice in America, such as removing "the effects of systemic racism not just from criminal justice, but from our economy, from health from housing and from our democracy itself."

"Sen. Warren, is that a substantial answer from Mayor Buttigieg?" Davis asked.

JUST WATCHED Warren calls out Buttigieg for not answering question Replay More Videos ... MUST WATCH Warren calls out Buttigieg for not answering question 01:29

"No," she replied to applause. "You have to own up to the facts."

Businessman Andrew Yang responded to Warren's statement about righting racial injustice by touting his Universal Basic Income plan to give every American $1,000 per month.

"With respect, you can't regulate away racism with a whole patchwork of laws that are race-specific," Yang said.

"We can't regulate that away through any other means except by putting money directly into the hands of African Americans and Latinos and people of color to allow businesses to actually flourish and grow in those communities," Yang said.

Biden touts foreign policy experience but fends off Iraq War criticism

Buttigieg, Biden and Sanders once again tangled over the former vice president's vote to authorize the use of force in Iraq when he was a senator from Delaware.

Buttigieg, who joined the US Naval Reserve in 2009 and served in Afghanistan, once again rebutted Biden's argument that he did not have enough experience by asserting that as a veteran he would have better judgment about whether to engage the US in combat.

"I believe that I have the judgment to help us get through these situations," Buttigieg said when asked whether he would have better judgment than Biden as commander in chief. "The vice president made the wrong decision when it came to such an important moment in our foreign policy."

Biden responded that his vote on the Iraq War was a mistake and repeated a false account of his support for the war begun under the George W. Bush administration.

"I trusted George Bush to keep his word. He said he was not going to go into Iraq. He said he was only using this to unite the United Nations to insist we get inspectors in to see what Saddam was doing," Biden said, referencing the false belief in the US at that time that Iraq had weapons of mass destruction.

JUST WATCHED Biden asks crowd to stand and applaud Lt. Col. Vindman Replay More Videos ... MUST WATCH Biden asks crowd to stand and applaud Lt. Col. Vindman 01:11

Biden noted that once he and President Barack Obama took office, "the President turned to me with the entire security apparatus, and said, 'Joe, I want you to organize getting 156,000 troops out of Iraq.' "

He touted his relationships with leaders around the world, noting he had taken part in major achievements including the Paris climate accord.

"I know every one of these world leaders by their first names." Biden said. "They call me. I talk to them. And I believe I can get it done."

In an impassioned moment, Biden urged the audience to stand and applaud Army Lt. Col. Alexander Vindman, the top Ukraine expert at the National Security Council , who testified during the House impeachment hearings. Trump had fired Vindman from his White House job earlier on Friday.

"I think we should all stand now and give Colonel Vindman a show of support," Biden said, throwing his hands above the podium. "Get up there!"

This story has been updated to reflect the full debate.