• Delegates can still change their minds before August 7.
• I know Trump's type, will put my record against his, says Harris.
• Harris as incompetent as Biden, says Trump campaign.

US Vice President Kamala Harris secured support Monday from a majority of delegates to the Democratic National Convention, likely ensuring she will become the party's nominee for president next month, according to multiple sources.

President Joe Biden threw his support behind Harris on Sunday when he withdrew from the race amid questions about his age and health. He pledged to remain in office as president until his term ends on January 20, 2025.

An Associated Press survey of delegates showed Harris had the support of 2,538 delegates, well beyond the 1,976 needed to win the delegates vote in the coming weeks. Democratic National Committee Chairman Jaime Harrison said on Monday the party will deliver a presidential nominee by August 7.

Delegates could still change their minds before August 7, but nobody else received any votes in the AP survey, and 57 delegates said they were undecided.

In Harris' first public appearance since the announcement, she rallied supporters on Monday with a debut campaign speech vowing to go after Republican nominee Donald Trump like the courtroom prosecutor she once was.

"I took on perpetrators of all kinds. Predators who abused women, fraudsters who ripped off consumers, cheaters who broke the rules for their own gain," Harris told campaign workers 28 hours after President Joe Biden, 81, abandoned the 2024 White House race and endorsed her.

"So hear me when I say I know Donald Trump's type. In this campaign, I will proudly, I will proudly put my record against his," said Harris, who was attorney general of California and a US senator before serving as Biden's vice president.

The Trump campaign responded to Harris' comments. "Kamala Harris is just as incompetent as Joe Biden and even more liberal," said Karoline Leavitt, the campaign's national press secretary. "Not only does Kamala need to defend her support of Joe Biden’s failed agenda over the past four years, she also needs to answer for her own terrible weak-on-crime record in California."

Trump is due to be sentenced in September after having been found guilty of falsifying business records to hide hush money payments to a porn star. He also faces criminal charges related to his efforts to overturn Biden's 2020 victory. He falsely claims he lost in 2020 because of election fraud.

Recovering from COVID-19 at his home in Delaware, Biden called into Harris' campaign event. He sounded hoarse but appreciative of his vice president.

Biden said he thought he had made the right decision by dropping out. The oldest person ever to occupy the Oval Office, Biden said on Sunday he would remain in the presidency until his term ends on January 20, 2025.

Harris, 59, outlined a series of policies she promised to pursue including signing laws to protect abortion rights and ban assault rifles and said she would make rebuilding the middle class the focus of her presidency.

Within minutes of receiving Biden's backing on Sunday, Harris began consolidating Democratic support for her presidential bid, securing commitments from hundreds of convention delegates, announcing a massive fundraising haul and earning endorsements from top party figures, Reuters was first to report.

These included former speaker Nancy Pelosi, who has remained influential since stepping down as the party's House of Representatives leader in 2022. The AFL-CIO labour union federation, which represents 12.5 million workers, said on Monday it had also endorsed Harris for president.

Harris' campaign said it raised $81 million in the 24 hours following Biden's exit, the most for a single day in the 2024 campaign for either party.

Virtually all of the prominent Democrats who had been seen as potential challengers to Harris have declared support for her, including Governors Gretchen Whitmer of Michigan, Gavin Newsom of California and Andy Beshear of Kentucky. Whitmer, in a post on X, on Monday said she would serve as co-chair of Harris' campaign.

Biden's departure was the latest shock to a White House race that included his disastrous June 27 debate performance against former President Trump and the July 13 near-assassination of Trump by a gunman during a campaign stop.

Harris lauded Biden for his service to the country. At a White House event to honour college athletes earlier on Monday, she said: "Joe Biden's legacy over the last three years is unmatched in modern history."

Harris will travel on Tuesday to Milwaukee, the largest city in the battleground state of Wisconsin, which last week hosted a Republican National Convention that offered a stark display of Trump's dominance over his party.

New generation

Harris, who is Black and Asian American, would fashion an entirely new dynamic with Trump, 78, offering a vivid generational and cultural contrast.

The Trump campaign has been preparing for her possible rise for weeks, sources told Reuters. It sent out a detailed critique of her record on immigration and other issues on Monday, accusing her of being more liberal than Biden.

It alleged that Harris favoured abolishing the US Immigration and Customs Enforcement agency and decriminalising border crossings, backed the so-called Green New Deal, supported the administration's electric vehicle mandates and encouraged "defund the police" efforts.

Some of those were positions Harris adopted as an unsuccessful presidential candidate in the 2020 election when she was running on a more liberal agenda than Biden but were not ones that the administration assumed, particularly with regard to border security and law enforcement issues.

Eric Holder, who was US attorney general in the administration of President Barack Obama, and his law firm Covington & Burling LLP will conduct the vetting of Harris' potential running mates, according to two sources familiar with the matter.

Trump, whose false claims that his 2020 loss to Biden was the result of fraud inspired the January 6, 2021, assault on the US Capitol, on Monday questioned Democrats' right to change candidates.

"They stole the race from Biden after he won it in the primaries," Trump said on his Truth Social platform.