Vice President Kamala Harris will campaign in the critical battleground state of Wisconsin for the first time as a presidential candidate on Tuesday after securing enough Democratic delegate support to clear a path to the nomination.

Harris quickly emerged as the Democratic candidate after President Joe Biden, 81, abandoned his reelection campaign on Sunday, following weeks of mounting pressure from members of his own party worried about his ability to beat former President Donald Trump or to serve for another four-year term.

Less than 36 hours after Biden endorsed Harris, she secured the nomination on Monday night by winning pledges from a majority of the delegates to next month's party convention who will determine the nomination, the campaign said.

"I am proud to have secured the broad support needed to become our party's nominee," Harris said in a statement. "I look forward to formally accepting the nomination soon."

An unofficial survey of delegates by the Associated Press showed Harris with more than 2,500 delegates, well over the 1,976 needed to win a vote in the coming weeks. Delegates could still change their minds, but no one else received any votes in the AP survey; 54 delegates said they were undecided.

Harris' rise dramatically reshapes an election in which many voters were unhappy with their options.

Saddled with concerns including his health and persistent high prices crimping Americans' household finances, Biden had been losing ground against Trump in opinion polls, particularly in the competitive states, known as swing states, that are likely to decide the election, including Wisconsin and the Sun Belt states of Arizona and Nevada.

The Wisconsin event offers another opportunity for Harris, the first Black woman and Asian American to serve as vice president, to reset the Democrats' campaign. She was due to speak in Milwaukee at 1 p.m. CDT (1800 GMT).

Harris, 59, offered a sense of how she plans to attack Trump on Monday, referring to her past of pursuing "predators" and "fraudsters" as San Francisco district attorney and California attorney general.

"So hear me when I say: I know Donald Trump's type," she said of her rival, who has a felony conviction and was found liable for sexual assault in civil court.

While a wave of senior Democrats have lined up behind Harris, the racial justice group Black Lives Matter on Tuesday challenged the party's swift move.

It called for a national virtual snap primary ahead of the Aug. 19-22 Democratic National Convention in Chicago, where the party will formally nominate its candidate.

"We call for the Rules Committee to create a process that allows for public participation in the nomination process, not just a nomination by party delegates," Black Lives Matter said in a statement to Reuters. "This moment calls for decisive action to protect the integrity of our democracy and the voices of Black voters."