The Democratic Party on Tuesday officially nominated former Vice President Joe Biden for the November presidential election showdown against Donald Trump, vowing to restore U.S. leadership on the global stage and revive relationships with long-standing allies.

"President Trump promised he would put 'America First' -- but Trump's America stands alone. Under his leadership, America's reputation and influence are in tatters," the party said in a policy platform adopted the same day, adding, "Democrats will not only repair our alliances, but reinvent them to advance mutual priorities and deal with new challenges."

Democratic presidential nominee former Vice President Joe Biden reacts in a video feed from Delaware after winning the votes to become the Democratic Party's 2020 nominee for president during the second night of the 2020 Democratic National Convention on August 18, 2020 in Milwaukee, Wisconsin. (Pool/Getty/Kyodo)

The nomination of the seasoned 77-year-old took place following a virtual roll call vote on the second day of the four-day Democratic National Convention, which has gone almost entirely online due to the coronavirus pandemic.

"Thank you very, very much from the bottom of my heart. It means the world to me and my family," said Biden, who is scheduled to deliver his official acceptance speech on Thursday.

Biden entered convention season maintaining a lead in national polls over Trump, 74, amid growing public disappointment over the current Republican administration's handling of the pandemic, which has so far seen around 170,000 deaths in the United States.

But a new CNN poll released Monday showed that the margin has narrowed substantially since June, suggesting the race remains fluid.

In its policy platform, the Democratic Party said the Trump administration has failed the American people in its response to the novel coronavirus, and also that it has "failed the world" by withdrawing funding and support for the World Health Organization during the pandemic.

If elected, Biden and the Democrats will take the "opposite tack" and drive a coordinated global health and economic response to the pandemic, such as by rejoining the WHO. It also said the United States will rejoin the Paris climate accord, which Trump exited due to his contention it treats the United States unfairly compared to countries like China.

Bearing in mind that Trump has sought to portray Biden as weak on China, the Democratic Party vowed to take "aggressive" action against China or any other country that tries to undercut U.S. manufacturing such as through unfair subsidies, and to "stand up" to Beijing's intellectual property theft and cyberespionage against U.S. companies.

The Democrats also pledged to resist the Chinese military's "intimidation" in the South China Sea, the waters of which Beijing claims almost entirely, and support the democratic rights of Hong Kong citizens as China tightens its grip on the former British colony.

But they also said they are opposed to "unilateral tariff wars" with China, while calling for the need to pursue cooperation with Beijing in areas of mutual interest like curbing the proliferation of nuclear weapons.

U.S. alliances, meanwhile, are "an irreplaceable cornerstone of our national security" and can also play a key role in efforts to push back against China's attempts to undermine international norms, the platform said.

Criticizing how Trump has eroded U.S. alliances such as by trying to "extort" South Korea to heavily increase its share of alliance costs amid the nuclear threat from North Korea, the Democrats said they will instead work to "strengthen ties with and between our key allies in the region, including Japan, South Korea, and Australia."

Turning to North Korea, the Democratic Party said it will seek to build "a sustained, coordinated diplomatic campaign to advance the longer-term goal of denuclearization."

Democratic presidential candidate former Vice President Joe Biden and his running mate Sen. Kamala Harris (D-CA) participate in a virtual fundraising event, in makeshift studio at the Hotel DuPont n August 12, 2020 in Wilmington, Delaware. (Getty/Kyodo)

On the economic front, the Democratic Party said it will reverse Trump administration tax cuts that have benefited the wealthiest Americans, work to raise the federal minimum wage and create jobs by investing in clean energy.

Through the convention, the Democratic Party is working to showcase Biden as an experienced and compassionate leader who can pull the country out of three ongoing crises -- the pandemic, the pandemic-induced recession and its long-standing racial injustice issues, which recently flared in the wake of the police killing of black man George Floyd.

Biden's bid for the Democratic presidential nomination follows unsuccessful runs in 1988 and 2008. He has vast foreign policy experience as a three-plus decade senator and as a former two-term vice president.

As a son of a used car salesman who grew up in a working-class neighborhood, Biden has touted himself as "middle-class Joe." At age 29, he became one of the youngest people ever elected to the Senate.

But weeks after he was elected, tragedy struck when he lost his first wife and infant daughter in a car accident. It has become a well-known episode that Biden, during his time as a single father and after marrying his current wife Jill, made a three-hour round-trip commute by train from his home state of Delaware to Washington, returning to tuck his sons into bed at night.

Later, he also lost his eldest son Beau, a rising star in Democratic politics, to brain cancer at the age of 46.

Biden's painful story has helped define his character as a person with compassion and empathy, which Democrats hope to contrast against Trump, more known for his inflammatory and divisive remarks.

Biden, however, is prone to verbal gaffes and his age is also considered a weakness. If elected, Biden would be the oldest U.S. president ever at the date of inauguration at age 78.

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