Democratic presidential candidate Kamala Harris will campaign alongside her new running mate, Tim Walz, on Wednesday, holding events in battleground states Wisconsin and Michigan that will offer an early test of his Midwestern credentials.

The trip to Eau Claire in Wisconsin and Detroit in Michigan is the first campaign swing for Walz, the governor of nearby Minnesota, whom Harris chose as her vice presidential pick on Tuesday in the biggest political decision of her nascent White House bid that has energized Democrats and shaken up the race.

The selection of Walz, an Army National Guard veteran and former teacher, adds geographic balance to a ticket with a Californian at the helm who needs a strong showing in the Midwest to win the Nov. 5 election.

A former congressman who won elections in a Republican-leaning district, Walz has a record of appealing to the white, rural voters who have increasingly turned to Donald Trump, this year's Republican presidential nominee, over the years.

Democrats regard Wisconsin and Michigan as near must-wins in the 2024 election, and they have loomed large for the party since Hillary Clinton's unexpected defeats there helped clinch Trump's 2016 win.

Biden beat Trump in both states in 2020, but polls showed him facing a close battle in Michigan before he dropped out of the race last month, with much of the state's significant Arab and Muslim American population fuming over his administration's support for Israel in its war against Hamas in Gaza following the Oct. 7 attacks.

The Republican vice presidential candidate, Senator JD Vance, was also set to speak in Eau Claire on Wednesday as part of a tour following Harris and Walz this week.

The Democratic trip is expected to include more than a half dozen states likely to determine the winner of the election, as the campaign aims to introduce Walz, who is not well known nationally.

At the pair's first rally together on Tuesday night in Philadelphia, Harris devoted much of her speech to highlighting Walz's background as a small town native, a high school social studies teacher and football coach and a Guardsman.

Walz, a folksy, affable speaker, nevertheless did not hold back on Trump and Vance, repeating his viral comment that they are "weird" and criticizing them over abortion, crime and the economy.

Harris' rise to the top of the Democratic ticket two weeks ago has dramatically reshaped the race. Polls show she has erased the lead that Trump had built during the final faltering weeks of Biden's campaign, and a re-energized Democratic Party has flooded her campaign with donations.

The Harris campaign said it raised more than $20 million on Tuesday after announcing Walz as the vice presidential pick.

Trump and Vance immediately cast Walz as too liberal, doubling down on criticism they have frequently leveled at Harris.

"This is the most Radical Left duo in American history," Trump wrote on his social media platform.

Vance, who spoke to reporters in Philadelphia hours before Walz's campaign debut, faulted the governor for his handling of protests after George Floyd, a Black man, was killed by a white police officer in 2020.

"The biggest problem with the Tim Walz pick, it's not Tim Walz himself. It's what it says about Kamala Harris - that when given the opportunity, she will bend the knee to the most radical elements of her party," Vance said.

Walz, who was first elected Minnesota governor in 2018, has pursued progressive policies, including free school meals, measures to combat climate change, middle class tax cuts and enhanced paid leave for workers.

Harris had considered several other candidates for her running mate, notably Pennsylvania Governor Josh Shapiro, who some Democrats had backed given the importance of his home state in November's election.