US vice president Kamala Harris and Minnesota governor Tim Walz will spend their first full day as running mates rallying Democrats across the American Midwest, a politically divided region that is crucial to their effort to win the White House in November.

The trip, which begins in Wisconsin before shifting to Michigan, is aimed at shoring up support among the younger, diverse, labour-friendly voters who were instrumental in helping President Joe Biden win the 2020 election.

But that coalition showed signs of fraying over the summer, particularly in Michigan, which has emerged as a focal point of Democratic divisions over Mr Biden’s handling of the Israel-Hamas conflict.

With Mr Biden now out of the race and Ms Harris officially the Democratic nominee, leaders of the Arab American community and key unions say they are encouraged by the choice.

Mr Walz’s addition to the ticket has soothed some tensions, signalling to some community leaders that Ms Harris heard concerns about another leading contender for the vice presidential slot, governor Josh Shapiro of Pennsylvania, who they felt had gone too far in his support for Israel.

“The party is recognizing that there’s a coalition they have to rebuild,” said Abdullah Hammoud, the mayor of Dearborn, Michigan. “Picking Walz is another sign of good faith.”

Wisconsin senator Tammy Baldwin, a Democrat seeking a third term, appeared with Ms Harris at a campaign stop there last month in suburban Milwaukee, and said in a fundraising email on Tuesday morning that she was “thrilled to see a fellow Midwesterner at the top of the ticket”.

Donald Trump had put a similar emphasis on appealing to voters in Midwestern states with his choice of Ohio senator JD Vance as his vice presidential choice.

Josh Shapiro
Pennsylvania governor Josh Shapiro had been thought as a potential to take on the role of running mate (AP)

Mr Vance will again bracket the Harris-Walz ticket with appearances in the same states on Wednesday. He is starting his day in Michigan before heading to Eau Claire, Wisconsin, the same city where the Democratic candidates will appear hours later before going to Michigan.

In Michigan, leaders say Democratic enthusiasm has surged since Ms Harris announced her candidacy.

That could be pivotal in Detroit, which is nearly 80% black, where leaders for months had warned administration officials that voter apathy could cost them in a city that is typically a stronghold for their party.

Ms Harris speaks at a campaign rally
Ms Harris has secured the Democratic nomination after Joe Biden decided not to pursue a second term (AP)

Rev Wendell Anthony, president of the NAACP Detroit branch, said the excitement in the city now is “mind-blowing”.

He likened it to Barack Obama’s first run for president in 2008, when voters waited in long queues to help elect the nation’s first black president.

The nation’s largest auto workers’ union, the United Auto Workers, also watched the vice presidential choice carefully.

They moved to endorse Ms Harris quickly after she stepped in to replace Biden, and UAW President Shawn Fain said publicly that she had a right to choose her own running mate. But he also said the union, which has 370,000 members and a huge presence in Michigan and other Midwestern states, didn’t favour Mr Shapiro, who had previously joined with Pennsylvania Republicans in calling for an expansion of voucher programmes that allow public tax dollars to flow to private schools.

Mr Fain had singled out Mr Walz – in addition to other candidates – for praise in an interview on August 2, saying the Minnesota governor was a “brilliant guy, sharp guy”.

On Tuesday, Mr Fain said Walz will make a “great vice president” and that he has “stood with the working class every step of the way”.