'I know Trump's type': Harris lashes out at Trump during her first campaign

US Vice President Kamala Harris has launched her election campaign with a blistering personal attack on Donald Trump and vowed to win in November despite the "rollercoaster" of President Joe Biden's shock exit.

As she closed in on the Democratic party's nomination on Monday with the support of a slew of heavyweights and massive voter donations, Harris lashed out at Trump in her first speech to campaign workers since Biden's announcement Sunday.

Biden, 81, meanwhile made his first public remarks for nearly a week as he recovers from Covid.

He called into the campaign meeting to say that dropping out — after mounting party and voter concerns over his health and mental acuity — had been the "right thing to do", and he praised Harris as "the best."

"We are going to win in November," a smiling Harris told campaign workers in her fiery speech at campaign headquarters in Wilmington, Delaware.

Turning her fire on Trump, Harris referred to her past role as California's chief prosecutor, saying she "took on perpetrators of all kinds."

"Predators who abused women. Fraudsters who ripped off consumers. Cheaters who broke the rules for their own gain. So, hear me when I say I know Donald Trump's type," she said to applause.

'Limitless optimism'

Biden dropped out on Sunday and endorsed Harris after three weeks of intensifying pressure triggered by a disastrous debate performance against Trump.

Aiming to become the first woman president in US history, the 59-year-old Harris won the backing of a seemingly unassailable number of Democrats.

Notably among them was powerful former US House speaker Nancy Pelosi, who said she endorsed Harris "with immense pride and limitless optimism."

The major AFL-CIO union federation also gave its formal endorsement on Monday.

Donors have rallied behind Harris, pouring a record $81 million into her campaign in the 24 hours after Biden stood aside.

The campaign claimed the haul was the largest one-day sum in presidential history — and that, among the 888,000 grassroots donors, some 60 percent were making their first 2024 contribution.

In his comments, Biden pledged to keep working on key topics, including ending the war in Gaza.

An aide to Harris later said she would meet with Israeli Prime Minister Benjamin Netanyahu this week during his Washington visit — separate from Biden's own planned sit-down.

Harris will not attend Netanyahu's address to Congress, the aide said, due to a previously scheduled event.

JD Vance fires back

Biden's stunning withdrawal has completely upended the 2024 race.

The move has jolted a demoralised Democratic party that Harris could now unify.

It has also hit Republicans hard, with former president Trump, 78 — now the oldest presidential nominee in US history — having to completely retool a strategy that had been built around attacking Biden over his age and physical frailty.

Harris' entry not only flips the age issue but puts Trump — a convicted felon also found liable for sexual assault — up against a woman and former prosecutor.

And Trump has seemingly found it hard to move on from Biden.

Republican vice presidential nominee JD Vance used his first solo campaign rallies to throw fresh barbs at Harris.

"History will remember Joe Biden as not just a quitter, which he is, but as one of the worst presidents in the history of the United States of America," Vance said in Virginia.

"But my friends, Kamala Harris is a million times worse, and everybody knows it. She signed up for every single one of Joe Biden's failures, and she lied about his mental capacity to serve as president."