Democratic presidential candidate Kamala Harris chose 60-year-old Minnesota Governor Tim Walz as her vice presidential running mate on Tuesday.

"We are going to build a great partnership. We are going to build a great team. We are going to win this election," Harris said on Instagram in a post announcing Walz as her VP pick. 

In a post on social media platform X after Harris announced the decision, Walz said: "I'm all in."  

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

US President Joe Biden appauded the choice as a "great decision" in a statement on X, formerly Twitter.

"The Harris-Walz ticket will be a powerful voice for working people and America's great middle class. 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," said the 81-year-old Democrat president, who endorsed his VP and former running mate Harris after deciding to step down from the race last month.

Who is Tim Walz? 

Walz, 60, is a former US Army National Guard member and teacher who has raised his profile recently, attacking Trump and Vance as "weird." The insult went viral and it has been embraced by the Harris campaign.

Walz is also a strong supporter of labor unions — an important part of the Democratic Party's electoral coalition. Walz was reportedly favored by both President Joe Biden and former Speaker Nancy Pelosi as Harris's VP pick.   

"Governor Walz doesn't just have the experience to be vice president, he has the values and integrity to make us proud," former President Barack Obama wrote in a statement after Walz was picked.   

By choosing Walz, Harris is hoping to better appeal to working-class and rural voters in the Midwest that could help her win against Donald Trump in the general election in November. Walz's interests in hunting, fishing, conservation and football could also attract voters who live in more rustic areas of the US heartland. 

The other contenders for vice president included Pennsylvania Governor Josh Shapiro, Kentucky Governor Andy Beshear, Illinois Governor JB Pritzker, US Senator Mark Kelly of Arizona and Transportation Secretary Pete Buttigieg.

Donald Trump's campaign on Monday labeled Walz as a "dangerously liberal extremist." Trump earlier chose Republican Senator JD Vance of Ohio as his vice presidential running mate. 

Where will the pair be headed?

Harris and Walz hit the campaign trail later in the day in Philadelphia, Pennsylvania. 

The Harris rally on Tuesday kicked off a five-day tour of key swing states — those with both a significant number of electoral college votes and where polls are close — likely to decide the election.

Harris and Walz will visit five cities after Philadelphia — Eau Claire, Wisconsin; Detroit, Michigan; Durham, North Carolina; Phoenix, Arizona; and Nevada's Las Vegas.

Why is the running mate being named now?

The announcement is being made after Harris formally secured the Democratic presidential nomination late on Monday, making her the first woman of color to lead the ticker of a major party.

The nomination became official after Democratic National Convention delegates ended a five-day round of online balloting on Monday

The party said 99% of delegates casting ballots had done so for Harris. A formal clarification of the vote will take place ahead of a celebratory roll call at the party convention later this month in Chicago.

Harris' securing of the nomination as the Democratic standard-bearer follows a turbulent and event-packed period for the party that began with resident Joe Biden's disastrous June debate performance.

After Biden announced his withdrawal, Harris came out of the blocks quickly to secure the backing of party delegates.

wd, rc/wmr (AP, AFP, dpa, Reuters)