Tim Walz makes campaign rally appearance after Kamala Harris chooses him as running mate

Team to embark on five-day, seven-city campaign blitz for November election

Democratic presidential nominee Kamala Harris and Minnesota Governor Tim Walz on Tuesday appeared at a campaign rally in Pennsylvania hours after she chose him as her running mate for the November election.

"Since the day that I announced my candidacy, I set out to find a partner who can help build this brighter future: a leader who will help unite our nation and move us forward; a fighter for the middle class; a patriot who believes, as I do, in the extraordinary promise of America," she told the crowd.

"I'm here today because I found such a leader."

Mr Walz is a former teacher, military veteran and union supporter who helped to enact an ambitious Democratic agenda for his state, including sweeping protection for abortion rights and help for families.

"He really does shine a light on a brighter future that we can build together," Ms Harris said.

"I'm telling you, Tim Walz will be ready on day one."

US Vice President Kamala Harris and Minnesota Governor Tim Walz appear together during a campaign event in Philadelphia, Pennsylvania. Getty Images / AFP

Ms Harris is hoping to shore up her campaign’s standing across the upper Midwest, a critical region in presidential politics that is often a buffer for Democrats seeking the White House.

Mr Walz thanked Ms Harris for the trust he has placed in him, "but maybe more so, thank you for bringing back the joy".

"I'm thrilled to be on this journey with you."

The new Democratic ticket members are pushing their middle-class backgrounds and capitalising on opportunity.

"The promise of America is what makes it possible for two middle-class kids: one, a daughter of Oakland, California, who was raised by a working mother; the other, a son of Nebraska parents, who grew up working on a farm," Ms Harris said.

"It's the promise of America, because only in America, only in America, is it possible for them together to make it all the way to the White House."

In a post on social media on Tuesday morning, Ms Harris said she was "proud to announce" her decision.

Ms Harris commended Mr Walz's "background both because it’s impressive in its own right, and because you see in no uncertain terms how it informs his record" of giving priority to families and dealing in bipartisanship.

Mr Walz broke into the political limelight recently when his description of Republican presidential candidate Donald Trump and vice presidential running mate, Ohio Senator JD Vance, went viral.

“That stuff is weird, they come across weird,” Mr Walz told MSNBC,and later repeated it at public events.

Calling far-right politicians and their language “weird” has now become a popular taunt among Democrats.

Ms Harris met the Governor on Sunday, and called Mr Walz on Tuesday morning about her decision and he accepted, AP reported.

"It is the honour of a lifetime to join Kamala Harris in this campaign," he said in a post on X. "I'm all in."

"Vice President Harris is showing us the politics of what’s possible. It reminds me a bit of the first day of school."

After the Pennsylvania event, the two are scheduled to embark on a five-day, seven-city tour of battleground states.

"Over those next 91 days and every day in the White House, let's all have Vice President Harris's back every single day, and we'll have yours," Mr Walz said to the crowd about the campaign and the future.

Ms Harris's search for a vice presidential running mate took place over only a few weeks after President Joe Biden ended his re-election bid – much shorter than the normal, months-long hunt.

The campaign gave former US attorney general Eric Holder's law firm the contract to vet candidates, poring over their past, careers and politics with interviews and research, Reuters reported.

Among those considered for the role were Transport Secretary Pete Buttigieg, Michigan Governor Gretchen Whitmer and Senator Mark Kelly.

The Vice President joined the presidential race in mid-July, when Mr Biden endorsed her for the Democratic Party nomination – a rare political shake-up in an election year but one that spurred excitement for Democrats.

Mr Biden said Ms Harris's move was "a great decision".

"The Harris-Walz ticket will be a powerful voice for working people and America's great middle class," he said in a post on X.

"They will be the strongest defenders of our personal freedoms and our democracy. And they will ensure that America continues to lead the world and play its role as the indispensable nation."

It is expected that the Democratic Party will formally accept Ms Harris's pick at its four-day convention in Chicago, Illinois, due to start on August 19.

She officially received the party nomination on Monday, formalising her campaign against former US president Mr Trump in the November 5 election.

"I stand before you today to proudly announce I am now officially the Democratic nominee for President of the United States," Ms Harris said in Philadelphia.

Mr Trump chose Mr Vance as his running mate in July.

"It's no surprise that San Francisco liberal Kamala Harris wants West Coast wannabe Tim Walz as her running-mate," Karoline Leavitt, the Trump campaign press secretary, said in a statement.

"If Walz don't tell voters the truth, we will. Just like Kamala Harris, Tim Walz is a dangerously liberal extremist, and the Harris-Walz California dream is every American's nightmare."

It is unclear if a vice presidential candidate debate will be scheduled after the previous Biden campaign and Trump team scrapped the original one.