MIAMI — Joseph R. Biden Jr. repeatedly found himself on the defensive in the Democratic debate on Thursday over his record as well as his personal views, with the most searing moment of the night, and the primary campaign to date, coming when Senator Kamala Harris confronted him over his comments on working with segregationists in the Senate.
Mr. Biden, the Democratic front-runner who was participating in his first major debate in seven years, was at times halting and meandering, but also forceful in pushing back on criticism of his record. Those attacks included a call for the 76-year-old former vice president to “pass the torch” to a younger generation, as well as questions about his positions on immigration and abortion, and his enthusiasm for working with Republicans.
But the most dramatic exchange was over not only policy — but also personal history. Peering down the stage to look at Mr. Biden directly, Ms. Harris assailed him for remarks he made this month invoking his work in a Senate that included a pair of notorious segregationists. She then went further, recalling that he had also opposed school busing in the 1970s.
“There was a little girl in California who was a part of the second class to integrate her public schools and she was bused to school every day,” Ms. Harris said. “And that little girl was me.”
Mr. Biden responded indignantly, calling her attacks “a mischaracterization of my position across the board” — and then returned fire at Ms. Harris, who has faced criticism from the left for her record as a prosecutor in California.
“If we want to have this campaign litigated on who supports civil rights and whether I did or not, I’m happy to do that,” he shot back. “I was a public defender, I didn’t become a prosecutor.”
[Read our analysis: Harris makes the case that Biden should pass the torch to her.]
The back and forth was the tensest moment in the first Democratic debates, which were split between Wednesday and Thursday, with 10 candidates each night, to accommodate the party’s sprawling field. And it illustrated both Mr. Biden’s vulnerability and the urgency his rivals feel to start sowing doubts about his candidacy with voters who mostly view him as Barack Obama’s vice president.
At a moment when President Trump has inflamed the country’s racial divisions, the clash also went to the heart of the Democrats’ debate over whom to nominate. Should they put forward a moderate who could appeal to some of the white voters who elected Mr. Trump but who also carries baggage from an earlier political era? Or would they be more likely to win by energizing younger and nonwhite voters with a candidate like Ms. Harris, a California senator whose father is black and mother was of Indian descent?
Ms. Harris’s offensive also represented an effort to jump-start her campaign, which started with great promise in January but has flagged as she has wrestled with whether to run as a progressive or appeal to her party’s moderate wing.
Her campaign has for months been privately consumed with Mr. Biden, whose initial advantage in the polls is partly attributable to his strong backing from African-Americans — votes Ms. Harris needs to win to secure the nomination. But it is Senator Elizabeth Warren of Massachusetts who has been gaining momentum of late.
Mr. Biden did not appear as unsteady as he has in some other recent public appearances, but he also may not have fully convinced Democrats that, as their nominee, he would be able to parry Mr. Trump’s hectoring attacks next year. Unlike some of the other candidates, he did not try to interject himself into the conversation.
But he did repeatedly recall his service with Mr. Obama, on whom he showered praise. And he flashed his sense of humor when Representative Eric Swalwell of California urged him to let a new generation of Democrats come forth.
“I’m still holding on to that torch,” Mr. Biden responded with a smile.
The former vice president has already faced a handful of other challenges, some of them, like allegations that he inappropriately touched women, before he even formally entered the race. And he has proved resilient, as many rank-and-file voters appeared less concerned about his transgressions than liberal activists were.
But those controversies were not broadcast on live television before millions of Americans.
It was not on matters of race alone that Mr. Biden found himself under biting attack. Rivals on both the left and the center dismissed Mr. Biden’s narrative of his political career as a case study in steady leadership, and repeatedly questioned the most fundamental proposition of his candidacy — that he is uniquely well suited to unite the country and wring progress from a sclerotic Washington.
When Mr. Biden delivered a laudatory account of his own skills as a congressional negotiator, boasting that he had coaxed a tax increase out of the Senate majority leader, Mitch McConnell, he earned a swift rebuke from a fellow moderate, Senator Michael Bennet of Colorado.
“The deal that he talked about, with Mitch McConnell, was a complete victory for the Tea Party,” Mr. Bennet said, arguing that Mr. Biden had made foolish concessions to Republicans on government spending without getting much in return. “That was a great deal for Mitch McConnell. It was a terrible deal for America.”
And without condemning Mr. Biden by name, Senator Kirsten Gillibrand of New York also rejected his deal-making ethos and called attention to his history of taking more conservative positions on abortion rights — including his past support for a ban on federal funding for abortion, known as the Hyde Amendment. Mr. Biden renounced his support for the measure only this month.
“When the door is closed, negotiations are made, there are conversations about women’s rights and compromises have been made on our backs,” Ms. Gillibrand said. “That’s how we got to Hyde. The how the Hyde Amendment was created — a compromise by leaders of both parties.”
It was Ms. Harris, however, who did the most to elevate her candidacy: At one point she was the top trending topic on Google in the country.
In addition to confronting Mr. Biden, she repeatedly chastised Mr. Trump, gently criticized Mr. Obama for his deportation policies and generally reminded Democrats why they were so intrigued about her candidacy in the first place.
Yet just as Ms. Warren did in the first debate on Wednesday, Ms. Harris also delighted Republicans by raising her hand to indicate her support for eliminating private health care in America, an issue on which she has struggled to explain her views in the past.
If Mr. Biden spent much of the debate on defense, so at times did the ascendant left wing of the Democratic Party, as a group of moderates led by Mr. Biden raised doubts — and repeatedly expressed something verging on alarm — about Democrats’ embrace of the far-left ideas pioneered by Senator Bernie Sanders of Vermont.
Mr. Biden rejected Mr. Sanders’s demand for a single-payer health care system and said that seeking to expand coverage more incrementally was the more pragmatic approach. Two lesser known rivals, Mr. Bennet and former Gov. John Hickenlooper of Colorado, introduced themselves to voters with stark warnings that Mr. Sanders and others who espouse his ideology could damage the Democratic Party and the country’s economy.
“If we don’t clearly define that we are not socialists,” Mr. Hickenlooper declared, “the Republicans are going to come at us every way they can and call us socialist.”
And Mayor Pete Buttigieg of South Bend, Ind., raised reservations about creating new universal college tuition benefits, suggesting that could end up providing unneeded financial support to wealthy students.
Yet Mr. Sanders had ample company onstage from Democrats aligned with his vision for health care and much more, including Ms. Harris and Ms. Gillibrand, both of whom raised their hands to endorse the replacement of private care with a “Medicare for all” system.
For his part, Mr. Sanders defended his agenda with plain enthusiasm. From his first comments of the night, he said voters were demanding “real change” from their government, and suggested without naming names that opponents like Mr. Biden were offering paltry half-measures.
Americans, Mr. Sanders said, deserve a president who will “stand up and tell the insurance companies and the drug companies that their day is gone, that health care is a human right.”
He did not, however, target the former vice president, and his familiar jeremiads were not met with the sort of enthusiastic applause from the audience as many of Ms. Harris’s lines.
Besides Mr. Biden and Mr. Sanders, a third prominent candidate, Mr. Buttigieg, spent a significant share of the debate explaining and defending his record in government. Having risen quickly in the polls as a favorite of educated liberal voters, Mr. Buttigieg has faced a difficult test over the past two weeks after a white police officer in South Bend shot and killed a black man.
Mr. Buttigieg acknowledged in a contrite statement that he had not achieved sufficient changes in the police department to avert similar episodes and to earn the trust of the African-American community there. Multiple rivals pounced, and Mr. Hickenlooper cast Mr. Buttigieg as a laggard in pursuing police reforms.
“We’re obviously not there yet,” Mr. Buttigieg conceded. “I accept responsibility for that because I’m in charge.”
Much like in Wednesday’s debate, nearly every candidate staked out a liberal position on immigration and expressed support for decriminalizing illegal migration.
[The latest data and analysis to keep track of who’s leading the race to be the Democratic nominee.]
Mr. Biden’s position on the issue was not entirely clear: He raised his hand along with most of the other candidates when they were asked whether they would support making illegal immigration a civil offense.
Yet when he was asked about the issue, he simply highlighted his efforts as vice president to send money to the Central American countries where many of the migrants are from, and he scorned Mr. Trump’s reversal of those policies.
“We all talk about these things,” he said. “I did it, I did it.”
Pressed on whether he would support deporting undocumented immigrants who have not committed any other offenses, Mr. Biden left himself some room.
“That person should not be the focus of deportation,” he said. A number of other candidates, including Ms. Harris, flatly said they would not deport such migrants.
Yet when the candidates were asked whether they wanted to include undocumented immigrants on government-run health care plans, Mr. Biden raised his hand.
To the surprise of exactly no one, President Trump sneaked a look at the Democratic debate in between meetings with world leaders in Osaka, Japan. And to the surprise of exactly no one, he professed not to be impressed.
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Mr. Trump evidently passed a television set just before joining Chancellor Angela Merkel of Germany. “All Democrats just raised their hands for giving millions of illegal aliens unlimited health care,” he (or perhaps an aide) quickly typed out on his Twitter account. “How about taking care of American Citizens first!? That’s the end of that race!”
Mr. Biden was not the only candidate who came under attack. Two low-profile candidates were just as pointed in their critiques of Mr. Sanders.
[We tracked down the 2020 Democrats and asked them the same set of questions. Watch them answer.]
Mr. Hickenlooper called Mr. Sanders’s “Medicare for all” proposal unrealistic. And Mr. Bennet noted that Mr. Sanders could not even get single-payer coverage passed in his own home state.
“Vermont rejected Medicare for all,” Mr. Bennet said.
Mr. Sanders rejected the attacks, noting that the polls show him faring well in a general election and arguing that the best way to defeat Mr. Trump was to expose his populist rhetoric as hollow — by providing voters with the genuine article.