Frontrunner Joe Biden faced repeated criticism on multiple fronts Thursday from his Democratic rivals for the 2020 presidential nomination, including calls to leave the battle to oust Donald Trump to a younger generation.
In a sometimes scrappy showdown of the Democratic heavyweights, Senator Kamala Harris landed several blows on Biden in the second of two nationally televised debates, putting the former vice president on the defensive as he argued that he is best-positioned to take on the Republican president.
Biden blasted Trump for his "horrible" policies that have exacerbated income inequality, while his chief rival for the nomination, Senator Bernie Sanders, took it directly to the "phony" president, calling him "a pathological liar and a racist."
But 76-year-old Biden also found himself on the receiving end of a pointed attack from a lower-tier candidate half his age.
Congressman Eric Swalwell, 38, called on him to "pass the torch" to a new generation better equipped to tackle climate change, expand health care coverage and reduce gun violence.
"I'm still holding on to that torch," Biden snapped back.
Several rivals were clearly seeking to wrench it from his grip, including Harris, the only black woman in the race, who made a stirring call for Biden to recognize his recent "hurtful" comments about being civil with avowedly segregationist US senators.
Biden, with the room dead quiet, insisted he does not "praise racists," and denied he opposed initiatives in the 1970s to bus children from predominantly black communities to better schools in more prosperous neighborhoods.
"There was a little girl in California who was part of the second class to integrate her public schools and she was bussed to school every day," Harris said, in one of the evening's most potent moments.
"That little girl was me."
- 'We are hurting' -
Another candidate in the upper tier, Pete Buttigieg, has also been on the back foot on racial issues following the fatal shooting of a black man by a white police officer in South Bend, Indiana, where he is mayor.
"When I look into his mother's eyes, I have to face the fact that nothing that I say will bring him back," Buttigieg said, adding that such tragedies are happening in communities across America.
"It's a mess. We are hurting."
With so many potential challengers to Trump, the party needed to split the top 20 candidates into debates over two nights in Miami, Florida.
Thursday's session featured four of the race's top five candidates in national polling, including Biden's main challenger Sanders, the 77-year-old US democratic socialist senator whose high-spending policies have pushed the party leftward in recent years.
Harris, 54, may have vaulted herself into serious contention with her composed performance and steely showdown with Biden.
But after the debate she stressed it wasn't personal.
"I otherwise have a great deal of respect for Joe Biden," she said. "I do not believe he is a racist."
Biden received no quarter from the old guard either.
When he was questioned about his support for the Iraq war and insisted that he took responsibility for getting 150,000 combat troops out of the country, Sanders pounced.
"Joe voted for that war, and I helped lead the opposition to that war, which was a total disaster."
Biden, seeking a recovery in his closing remarks, called for restoration of "the "soul" of the country after Trump "ripped it out."
"We have got to unite the United States of America," he added.
- 'State-sponsored crimes' -
All candidates savaged Trump for his immigration policy, including Senator Kirsten Gillibrand who said the president had "torn apart our moral fabric" by separating migrant children from their parents at the border.
Author Marianne Williamson, a surprise presidential candidate, branded the policies "state-sponsored crimes."
When all contenders signalled support for undocumented immigrants' access to health care, Trump, who has made stopping illegal immigration a centerpiece of his presidency, weighed in from the G20 summit in Japan.
In a tweet he accused Democrats of supporting "giving millions of illegal aliens unlimited healthcare. How about taking care of American Citizens first!?"
Debate also addressed whether the party should embrace a shift towards more liberal policies and government involvement in the economy.
On Wednesday third-placed Elizabeth Warren called out disparities in wealth and income and pledged to work to improve the lives of struggling families.
Sanders covered the same ground Thursday, but he also acknowledged that, in a shift to his Medicare for All platform, Americans would have to pay more taxes.