US Vice President Kamala Harris speaks at her Presidential Campaign headquarters in Wilmington, DE, US, July 22, 2024. (Photo:REUTERS)

Harris has become the party's presumed nominee after President Joe Biden withdrew from his re-election campaign on Sunday. Less than 36 hours after Biden endorsed Harris, she secured the nomination on Monday night by winning the pledged support of a majority of the party's delegates who will determine the nomination, the campaign said.

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.

The Wisconsin trip offers another opportunity for the 59-year-old former California prosecutor to reset the Democrats' campaign and make the case that she is best positioned to compete with Donald Trump.