Kamala Harris is heading to the battleground state of Wisconsin for her first 2024 United States presidential campaign rally, as the likely Democratic nominee’s push for the White House picks up steam.

Harris will hold a rally in Milwaukee on Tuesday, two days after President Joe Biden dropped out of the race following weeks of questions about his age and fitness to serve another term in office.

While the US vice president has not officially been confirmed as the Democratic Party’s presidential nominee, The Associated Press news agency reported on Monday evening that Harris had secured enough votes from delegates to secure the nomination.

“When I announced my campaign for President, I said I intended to go out and earn this nomination. Tonight, I am proud to have secured the broad support needed to become our party’s nominee,” she said in a statement.

Harris’s candidacy has reinvigorated a US election campaign that had failed to captivate many voters who were frustrated by a choice between Biden and former President Donald Trump as well as by the state of the economy, American foreign policy and other issues.

Since Biden’s decision on Sunday to forgo his re-election bid, Harris has garnered the backing of top Democrats, including former House of Representatives Speaker Nancy Pelosi and Governors Gretchen Whitmer of Michigan and Gavin Newsom of California.

Her campaign also said it had collected more than $100m in contributions from Sunday afternoon to Monday evening with 62 percent of all donations coming from first-time donors.

Tonight, I am proud to have earned the support needed to become our party’s nominee.

Over the next few months, I’ll be traveling across the country talking to Americans about everything on the line. I fully intend to unite our party and our nation, and defeat Donald Trump. pic.twitter.com/Bsq3N6pMAi

— Kamala Harris (@KamalaHarris) July 23, 2024

Reporting from the White House on Tuesday morning, Al Jazeera’s Kimberly Halkett said Harris’s candidacy has injected “enormous” excitement into the Democratic presidential race.

“What we’ve seen is just record-breaking fundraising,” said Halkett, adding that tens of thousands of people also have signed up to work on the vice president’s campaign.

Halkett explained that Harris’s team is concentrating on four key US states – Nevada, Arizona, Georgia and Pennsylvania – as well as on younger voters of colour across the country as she prepares to face Trump, the Republican candidate, in November’s election.

Wisconsin, which is where the Republican Party held its national convention last week, is also expected to be critical in the race for the White House.

“There are independents and young people who did not like their choices, and Harris has a chance to win them,” Paul Kendrick, executive director of the Democratic group Rust Belt Rising, told the Reuters news agency.

Meanwhile, Trump and his vice-presidential running mate, Senator JD Vance, have been lambasting Harris, with the former US president attacking her record and dubbing her “Lyin’ Kamala” on his Truth Social platform.

Republicans also have tried to blame Harris for the high number of migrants and asylum seekers crossing the US-Mexico border during Biden’s term in office – a key election issue – and called her the administration’s “border czar”.

But experts have slammed that criticism as false and noted that Harris is not in charge of US border policies. Biden tasked her in 2021 with addressing the “root causes” of migration to the US from Central America.

For her part, Harris has hit back at Trump and stressed some of the key issues she plans to campaign on, namely access to reproductive healthcare, economic opportunity and a defence of democratic institutions.

In a speech to campaign staff and volunteers in Delaware on Monday, Harris said US voters face a choice in November between “two different visions” for the country: “one focused on the future, the other focused on the past”.

The former California attorney general also said her history of prosecuting “predators”, “fraudsters” and “cheaters” would serve her well in the campaign.

“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,” Harris said.

Trump has been convicted of falsifying business records, found civilly liable for sexually abusing a magazine columnist and indicted in two criminal cases related to efforts to overturn the results of the 2020 election.

He has rejected any wrongdoing and said he is the victim of a politically motivated “witch-hunt”.