Democrats formally nominate Joe Biden

Joe Biden was formally nominated as the Democratic Party's presidential candidate on Tuesday, as former presidents Jimmy Carter and Bill Clinton highlighted integrity and responsibility among the top traits for a future American leader.

The former vice-president became his party's nominee on the second day of the virtual Democratic National Convention as a prerecorded roll call vote from delegates in all 50 states and US territories was aired at the beginning of Tuesday night's program, with a "leadership matters" theme. Biden, 77, will deliver his acceptance speech on Thursday night.

"Donald Trump says we're leading the world. Well, we are the only major industrial economy to have its unemployment rate triple," Clinton, US president from 1993 to 2001, said in excerpts of his remarks released in advance.

"At a time like this, the Oval Office should be a command center. Instead, it's a storm center. There's only chaos. Just one thing never changes — his determination to deny responsibility and shift the blame. The buck never stops there," the 42nd president said.

Clinton, who will be 74 on Wednesday, prerecorded his address from his home in Chappaqua, New York, north of New York City.

Bill Clinton's tone seemed like that of a speech made Monday night by former first lady Michelle Obama, which featured a scathing attack on President Donald Trump.

The Democratic Party's choice is a down-to-earth and go-to-work president who takes responsibility, not shifts the blame; unites, not divides, and that choice is Biden, according to Clinton.

Another heavy hitter to appear virtually at the convention program was former president Carter, who also noted that the country deserves a leader with integrity and judgment, someone who is "honest and fair".

"Joe has the experience, character, and decency to bring us together and restore America's greatness," said Carter, now aged 95.

The convention also introduced Jill Biden to the nation as the prospective first lady.

"How do you make a broken family whole? The same way you make a nation whole. With love and understanding — and with small acts of compassion. With bravery. With unwavering faith," said the former second lady, according to advance remarks.

Trump, 74, vented his disapproval of the criticism heaped on him from the opening night of the convention. He tweeted Tuesday, "People forget how divided our Country was under Obama Biden. The anger and hatred were unbelievable. They shouldn't be lecturing to us. I'm here, as your President, because of them!"

The Democrats need to use the quadrennial gathering to lay out a vision for the future that appeals to a broad swath of voters, make the case against Trump and his down-the-line congressional supporters without turning off suburban Republicans and independents, William A. Galston and Elaine Kamarck, both senior fellows of Governance Studies at the Brookings Institution, said in a research note.

Hillary Clinton, former US secretary of state and first lady, said prior to the convention that if Biden and Harris win, the work before them will be "rather overwhelming".

In an video talk with the Atlantic Council broadcast on Monday, Clinton called US ties with China the "most consequential of our global relationships" and predicted that a Biden-Harris administration would aim to set the US "relationship with China back on a steadier, more predictable course".

Biden's vice-presidential pick, Senator Kamala Harris of California, will headline Wednesday night's program along with former president Barack Obama.

To take attention from the Democrats, Trump traveled to the border city of Yuma in the hotly contested state of Arizona on Tuesday afternoon to focus on what his re-election campaign said are Biden's "failures on immigration and border security".

On Monday night, former first lady Michelle Obama opened her remarks for the convention with, "You know, I hate politics". But then she proceeded to skewer Trump on immigration, race relations, the novel coronavirus pandemic, the economy and what she said was his lack of empathy.

Trump is the "wrong president for our country", she said in pretaped remarks, adding that he is "clearly in over his head".

"If you think things cannot possibly get worse, trust me, they can, and they will, if we don't make a change in this election," she said. "If we have any hope of ending this chaos, we have got to vote for Joe Biden like our lives depend on it."

Trump responded Tuesday with a series of tweets that reiterated his attacks on his predecessor and Biden, Obama's vice-president.

"Somebody please explain to @MichelleObama that Donald J. Trump would not be here, in the beautiful White House, if it weren't for the job done by your husband, Barack Obama. Biden was merely an afterthought," he wrote on Twitter.

Trump also criticized the Obama administration's handling of the 2009 H1N1 swine flu outbreak. About 12,000 people died in the US from H1N1, statistics show, compared to more than 171,000 US deaths from the COVID-19 pandemic still underway, according to Johns Hopkins University data.

US Senator Bernie Sanders of Vermont, who was Biden's chief rival for the nomination, urged his supporters to get behind Biden despite their policy differences.

The Republican National Convention, also largely virtual, takes place next week. Trump will give his acceptance speech at the White House, despite criticism he is politicizing the presidential residence.

Ai Heping in New York contributed to this story.