As the Democratic Party continues to coalesce around her, Harris is travelling to Milwaukee, where she will hold her first campaign rally since she launched her campaign on Sunday with Biden's endorsement.
Harris has raised more than $US100 million ($A150 million) since Sunday afternoon and has scored the backing of Democratic officials and political groups.
Tuesday's visit was scheduled before Biden ended his campaign but it took on new resonance as Harris prepared to take up the mantle of her party against Trump and looks to project calm and confidence after weeks of Democratic Party confusion over Biden's political future.
The visit comes a week after the Republican National Convention wrapped up in the city and as Harris works to sharpen her message against the Republican nominee with just more than 100 days until the election.
Wisconsin is part of the Democrats' "blue wall" of Michigan, Wisconsin and Pennsylvania that is critical to their 2024 plans.
Vice-President Kamala Harris, pictured with husband Douglas Emhoff, will campaign in Wisconsin. (AP PHOTO)
The vice-president previewed the themes that will be prominent in her campaign against Trump on Monday during a stop at her campaign headquarters in Wilmington, Delaware, contrasting her time as a prosecutor with Trump's felony convictions - "I know Donald Trump's type," she said - and casting herself as a defender of economic opportunity and abortion access.
"This election will present a clear choice between two different visions. Donald Trump wants to take our country back to a time before many of us had full freedoms and equal rights," she said in a statement.
"I believe in a future that strengthens our democracy, protects reproductive freedom and ensures every person has the opportunity to not just get by, but to get ahead.
"I am grateful to President Biden and everyone in the Democratic Party who has already put their faith in me, and I look forward to taking our case directly to the American people."
By Monday night, Harris, s, who also ran for president in 2020,, had the support of well more than the 1976 delegates she will need to win on a first ballot, according to the AP tally of delegates.
No other candidate was named by a delegate contacted by the AP.
Still, the AP is not calling Harris the new presumptive nominee.
That is because the convention delegates are still free to vote for the candidate of their choice at the convention in August or if Democrats go through with a virtual roll call ahead of that gathering in Chicago.
The tally is based on interviews with individual delegates, public statements from state parties, many of which have announced that their delegations are supporting Harris en masse, and public statements and endorsements from individual delegates.
Harris was to be joined by major elected officials in Wisconsin, including Governor Tony Evers, senator Tammy Baldwin, Lieutenant Governor Sara Rodriguez, Attorney-General Josh Kaul, Secretary of State Sarah Godlewski and Wisconsin Democratic Party Chair Ben Wikler, as well as state union leaders.
