Updated at 3:40 p.m. ET

Hillary Clinton has officially thrown her support behind Joe Biden in the 2020 presidential race against President Trump, who defeated Clinton in 2016.

The 2016 Democratic nominee and former secretary of state announced the endorsement in an online town hall with Biden on Tuesday afternoon to discuss the impact of COVID-19 on women. It's the latest high-profile endorsement racked up by the former vice president, following House Speaker Nancy Pelosi on Monday.

"Just think of what a difference it would make right now if we had a president who not only listened to the science, put facts over fiction, but brought us together, showed the kind of compassion and caring that we need from our president, and which Joe Biden has been exemplifying throughout his entire life," Clinton said.

"Think about what a difference it would make if we had a real president, not just one who played one on TV," she added, criticizing the Republican opponent who defeated her in 2016.

Clinton has a unique experience with Trump, narrowly losing the 2016 race against the real estate developer and former reality TV star, despite winning the popular vote.

The loss marked a stunning cap to a decades-long political career that saw Clinton serve as the third female secretary of state and the first female presidential nominee of a major political party.

Her 2016 defeat also galvanized a constituency of progressive women supporters to launch the worldwide 2017 Women's March protests.

However, for all her remaining goodwill among Democrats, Clinton remains a polarizing figure, with many blaming her numerous political missteps and moderate voting record for failing to inspire a more robust turnout in the 2016 race.

Still, Clinton's endorsement could help consolidate Democrats around Biden, who faces many of the same criticisms weathered by Clinton in her White House pursuit. Biden considered running against Clinton in 2016, but decided against it in the wake of his son's death from cancer.

Both served in President Barack Obama's administration and the U.S. Senate. And their respective Senate voting records have come under scrutiny for representing ideals of a bygone Democratic Party, which have been rejected by many younger progressives as centrist and non-inclusive.

Biden's campaign hopes that Clinton's endorsement, as well as recent endorsements by fellow Democratic Party heavyweights like former President Barack Obama and Vermont Sen. Bernie Sanders, will energize voters from the various party factions to claim a victory for Democrats in the Nov. 3 election.

In introducing Clinton in the Tuesday town hall, Biden called his former Senate and White House colleague "my friend, the former senator, former secretary of state, and the woman who should be president."

Also on Tuesday, a number of top Sanders supporters announced the formation of a super PAC to energize progressive support for Biden. Sanders and Clinton had a particularly rancorous primary battle in 2016, the wounds of which never completely healed.

Sanders has swiftly and vocally come around to support Biden since dropping out as his main challenger in the primary, a sharp contrast to how the party remained fractured four years ago.

The Trump campaign quickly responded to Clinton's endorsement with a statement on Tuesday afternoon.

"There is no greater concentration of Democrat establishment than Joe Biden and Hillary Clinton together," Trump campaign manager Brad Parscale said in a statement. "Both of them carry the baggage of decades in the Washington swamp and both of them schemed to keep the Democrat nomination from Bernie Sanders. President Trump beat her once and now he'll beat her chosen candidate."

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