Washington DC - Kamala Harris' presidential campaign said Sunday that it has raised more than half a billion dollars in just over a month, "a record for any campaign in history."

The eye-watering amount of $540 million, raised since Harris launched her campaign after President Joe Biden dropped out of the White House race on July 21 and endorsed her, comes as she and Republican rival Donald Trump embark on the final 10-week sprint to election day on November 5.

Trump, whose campaign was thrown when Biden stepped aside, reported having $327 million cash on hand at the start of August.

Just before Harris took to the stage at the DNC on Thursday to accept her party's nomination, "we officially crossed the $500 million mark," campaign chair Jen O'Malley Dillon said in a memo.

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"Immediately after her speech, we saw our best fundraising hour since launch day," she continued.

"In just over a month since we launched our campaign, Team Harris-Walz raised $540 million – a record for any campaign in history."

The sum reflects funds raised across the campaign, the Democratic National Committee, and joint fundraising committees, the statement said.

One-third of those donations were from first-time contributors, O'Malley Dillon said.

Harris' campaign appears to have energized large and small donors alike – a turnaround from the uncertain period after a disastrous Biden debate performance in June, when major donors reportedly halted fundraising.

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It also appears to have mobilized what O'Malley Dillon called "a virtual army of volunteers," with the convention seeing grassroots workers signing up in droves.

"Meanwhile, Donald Trump's battleground infrastructure remains incredibly sparse," she said.

Harris and Trump are neck and neck in the polls less than three weeks before their September 10 debate in Philadelphia.

Harris, a 59-year-old former senator from California and prosecutor, left the Democratic convention in Chicago with momentum, having outraised Trump and erased the polling leads he enjoyed before she replaced Biden on the Democratic ticket.

The vice president also faced mass protests inside and outside the convention over the Biden-Harris administration's ongoing military support for Israel's attacks on Gaza.