The contenders for US vice-president have clashed over the coronavirus pandemic in their only debate ahead of next month's election.
Democrat Kamala Harris called Donald Trump's handling of the pandemic "the greatest failure of any presidential administration" in history.
Vice-President Mike Pence, a Republican, said the Democratic Party's pandemic plan amounted to "plagiarism".
Democratic nominee Joe Biden leads Mr Trump with 26 days to go to the vote.
Opinion polls indicate the Republican president is trailing by single digits in a handful of battleground states that will decide who wins.
Vice-presidents have tie-breaking power in the Senate and are required to step in if a president is unable to perform their duties. Their day-to-day responsibilities vary with each administration, but they typically serve as top advisers and some take on specific policy portfolios.
Wednesday night's meeting was a civil debate between two smooth communicators compared to last week's belligerent showdown between Mr Trump and Mr Biden, which degenerated into insults and name-calling.
Mr Pence did not interrupt as much as the president last week, but when he did, Ms Harris interjected: "Mr Vice-President, I'm speaking, I'm speaking."
The viral moment on Wednesday was a fly landing on Mr Pence's head and remaining there for some two minutes.
But there were heated exchanges.
What was the main talking point?
The 90-minute televised debate at the University of Utah in Salt Lake City was marked by disagreements over the Trump administration's handling of the pandemic.
Ms Harris accused Mr Pence and the president of deliberately misleading Americans about the lethality of coronavirus.
"They knew, and they covered it up," she said, adding that they had "forfeited their right to re-election".
Mr Pence accused the Biden-Harris campaign of copying the White House's pandemic strategy, alluding to a blunder that ended Mr Biden's 1987 run for the presidency when he plagiarised a speech by then-British Labour leader Neil Kinnock.
Ms Harris was asked by the moderator whether she would take an approved Covid-19 vaccine distributed ahead of the election.
The 55-year-old California senator said she would not take a jab touted by Mr Trump without the say-so of medical professionals.
Mr Pence, who heads the White House coronavirus task force, retorted: "The fact that you continue to undermine public confidence in a vaccine if the vaccine emerges during the Trump administration I think is unconscionable."
The plexiglass barriers separating the two debaters seated 12ft (3.6m) apart were a vivid reminder of the pandemic that has killed more than 200,000 Americans.
The president - who is himself recovering from the virus - returned to the White House on Monday evening after three nights in hospital, with his opinion poll numbers drooping.
On Wednesday he declared that catching the disease was a "blessing from God" that exposed to him to experimental treatments he vowed would become free for all Americans.
The virus, meanwhile, has spread through the West Wing of the White House and infected figures inside the president's re-election campaign.
ABC News reported that an internal government memo, dated Wednesday, said "34 White House staffers and other contacts" had been infected in recent days.
The White House has not yet commented on this.
No standout winner but Democrats will be happy
Vice-presidential debates seldom shake up presidential races, and the face-off between Kamala Harris and Mike Pence on Wednesday night seems destined to be no different.
Both candidates had strong moments, and a few stumbles, over the course of the 90-minute affair. But as far as lasting memories go, they were few and far between.
If this was a match that showcased the futures of the Democratic and Republican parties, the real fireworks will have to wait for the coming years.
An unmemorable result, in and of itself, is good news for the Democrats and Joe Biden, who polls suggest are leading in the race. One more campaign set-piece in the books, and one step closer to election day.
What were the other key moments?
On the question of racial justice, Mr Pence expressed shock at the killing of George Floyd in Minnesota. But he added: "There is no excuse for the rioting and looting that followed."
He pointed to one of his guests in the auditorium, Flora Westbrooks, a black woman whose hair studio was destroyed during unrest in Minneapolis.
He said Mr Biden and Ms Harris's claim that America is systemically racist and that police have an implicit bias against minorities is "a great insult".
Ms Harris - who was making history by becoming the first black woman to stand on a vice-presidential debate stage - said: "Last week the president of the United States took a debate stage in front of 70 million Americans and refused to condemn white supremacists."
"Not true, not true," said Mr Pence, arguing that when Ms Harris was a prosecutor in San Francisco African Americans were more likely to be prosecuted for minor drug offences than whites or Latinos.
In other key flashpoints:
- Ms Harris said the Trump tit-for-tat tariffs on China had caused a manufacturing recession, adding: "You lost that trade war. You lost it." Mr Pence hit back: "Lost the trade war with China? Joe Biden never fought it. Joe Biden's been a cheerleader for communist China through... the last several decades"
- Ms Harris assailed Mr Trump for paying $750 a year in federal income taxes as president, according to a New York Times investigation. "When I first heard about it, I literally said, 'You mean $750,000?' And it was like, 'No, $750'"
- Ms Harris said Mr Trump had "betrayed our friends and embraced dictators around the world". Mr Pence said Mr Trump had ordered operations that killed Islamic State leader Abu Bakr al-Baghdadi and top Iranian general Qasem Soleimani
What questions did they dodge?
The debate was notable for the questions that the candidates did not directly answer.
Mr Pence twice pressed Ms Harris on whether Mr Biden would expand the number of seats on the Supreme Court, which has had nine justices for a century and a half, but she spoke instead about Mr Trump's current judicial nominee.
The Constitution does not say how many justices there must be on the Supreme Court, so if a president and Congress were to agree they could change the law to expand or shrink it.
Some Democrats have suggested doing this amid arguments over Mr Trump's nominee, whose confirmation would cement a right-leaning majority on the top court. Mr Biden has not said whether he would support expanding the court if he became president.
Mr Pence - a mild mannered former Indiana governor known for his steadfast loyalty to Mr Trump - did not answer questions about whether he would want his home state of Indiana to ban abortion, or how the Trump administration would ensure medical coverage for sick Americans.
Focus on the running mates has intensified given 74-year-old Mr Trump's Covid-19 diagnosis, and the fact that Mr Biden would be the oldest president ever to take office at 78.
But when asked by the debate moderator about the chances of them taking over the presidency, both candidates skirted the subject.
Mr Pence, 61, assailed Mr Biden's handling of the 2009 swine flu outbreak, and Ms Harris - the daughter of an Indian mother and a Jamaican father - spoke of her own biography.
What did voters think?
Shloka Ananthanarayanan (Democrat): "I wouldn't necessarily say there was one moment that stood out, but what stood out was the tone and the fact that no one was yelling at each other during this debate."
Jim Sullivan (Republican): "Given the age of the two candidates, the vice-presidential pick this time around is pretty significant. Last week was just distressing, so this was a real breath of fresh air. I don't agree with Kamala Harris on a lot of things, but they both handled themselves well and I liked the format."
Akayla Sellers (Democrat): "They could have discussed a lot more in depth about healthcare, education and the racial uproar. You see a lot of people crowding the streets, they are the younger generation and they didn't discuss that in depth."
Gordon Kou (Republican): "They did a better job of defending their candidates than the actual candidates did. Overall, the winner was America because we somewhat saved face after the debacle last week."