PHILADELPHIA — Kamala Harris introduced Minnesota Gov. Tim Walz to the nation at a raucous rally Tuesday in Philadelphia aimed at building momentum for the newly minted Democratic presidential ticket in the sprint toward Election Day.

“He’s the kind of person who makes people feel like they belong and then inspires them to dream big. ... That's the kind of vice president America deserves,” Harris said.

Taking the microphone after Harris, Walz revved up the crowd for the rigorous campaign to come. “We’ve got 91 days. My God, that's easy. We'll sleep when we’re dead,” he said.

The remarks reflected the urgency of the moment, with Harris tapping Walz for the ticket during one of the most turbulent periods in modern American politics. Republicans have rallied around former President Donald Trump after he was targeted in an attempted assassination in July. Just days later, President Joe Biden ended his reelection campaign, forcing Harris to scramble to unify Democrats and decide on a running mate over a breakneck two-week stretch.

In choosing the 60-year-old Walz, Harris is elevating a Midwestern governor, military veteran and union supporter who helped enact an ambitious Democratic agenda for his state, including sweeping protections for abortion rights and generous aid to families.

It was her biggest decision yet as the Democratic nominee and she went with a broadly palatable choice — someone who says politics should have more joy and who deflects dark and foreboding rhetoric from Republicans with a lighter touch, a strategy that the campaign has been increasingly turning to since Harris took over the top spot.

Harris hopes Walz will help her shore up her campaign’s standing across the upper Midwest, a critical region in presidential politics that often serves as a buffer for Democrats seeking the White House. The party remains haunted by Trump's wins in Michigan and Wisconsin in 2016. Trump lost those states in 2020 but has zeroed in on them as he aims to return to the presidency this year and is expanding his focus to Minnesota.

Since Walz was announced, the team raised more than $10 million from grassroots donations, the campaign said.

Walz is far from a household name. An ABC News/Ipsos survey conducted before he was selected but after vetting began showed that nearly 9 in 10 U.S. adults did not know enough to have an opinion about him.

Harris devoted much of her speech to telling the audience about Walz’s life and work, which included stints as a social studies teacher and a football coach.

“To those who know him best, Tim is more than a governor,” she said.

Harris, the first Black woman and person of South Asian descent to lead a major party ticket, initially considered nearly a dozen candidates before zeroing in on a handful of serious contenders.

Trump has focused much of his campaign on appealing to men, emphasizing a need for strength in national leadership and even featuring the wrestler Hulk Hogan on the final night of the Republican National Convention. Harris’ finalists — all white men — marked an acknowledgment of the Democrat’s need to at least try to win over some of that demographic.

She personally interviewed three finalists: Pennsylvania Gov. Josh Shapiro, Arizona Sen. Mark Kelly and Walz. Harris wanted someone with executive experience who could be a governing partner, and Walz also offered appeal to the widest swath of the diverse coalition.

His selection drew praise from lawmakers as ideologically diverse as progressive leader Rep. Alexandria Ocasio-Cortez, D-N.Y., and independent Sen. Joe Manchin of West Virginia, a moderate who left the Democratic Party earlier this year.

A team of lawyers and political operatives led by former Attorney General Eric Holder pored over documents and conducted interviews with potential selections. Harris mulled the decision over on Monday with top aides and finalized it Tuesday morning, according to three people familiar with Harris' decision who spoke on condition of anonymity to describe private deliberations.

Shapiro, an ambitious politician in his own right, struggled with the idea of being No. 2 at the White House and said he felt he had more to do in Pennsylvania, according to one of the people familiar with Harris' decision. There was also public pushback to Shapiro for his stance on Israel from Arab American groups and younger voters angry over the administration's response to the Israel-Hamas war.

The other contenders threw their support behind the ticket Tuesday, and Shapiro was one of the speakers at Tuesday's Philadelphia rally. Biden described the Harris and Walz ticket as “a powerful voice for working people and America's great middle class.”

Walz coined one of Democrats’ buzziest campaign bits to date, calling Trump and his running mate Ohio Sen. JD Vance “just weird,” a label that the Democratic Governors Association — of which Walz is chairman — amplified in a post on X and Democrats more broadly have echoed.

During a fundraiser for Harris on Monday in Minneapolis, Walz said: “It wasn’t a slur to call these guys weird. It was an observation.”

Harris, second gentleman Doug Emhoff and Walz will spend the next five days touring critical battleground states, visiting Wisconsin and Michigan on Wednesday and Arizona and Nevada later in the week.

Vance, for his part, planned stops in some of the same areas. He said Tuesday that he called Walz earlier in the day and left a voice message.

The Trump campaign on Tuesday immediately tried to tag Walz as a far-left liberal.

“It’s no surprise that San Francisco Liberal Kamala Harris wants West Coast wannabe Tim Walz as her running-mate — Walz has spent his governorship trying to reshape Minnesota in the image of the Golden State,” said Karoline Leavitt, Trump's campaign press secretary. “Walz is obsessed with spreading California's dangerously liberal agenda far and wide.”

Walz, who grew up in the small town of West Point, Nebraska, was a teacher, coach and union member at Mankato West High School in Minnesota before entering politics.

He won the first of six terms in Congress in 2006 from a mostly rural southern Minnesota district and used the office to champion veterans issues. Walz served 24 years in the Army National Guard, rising to command sergeant major, one of the highest enlisted ranks in the military, although he didn't complete all the training before he retired so his rank for benefits purposes was set at master sergeant.

He ran for governor in 2018 on the theme of “One Minnesota” and won by more than 11 points.

David Ivory, a 46-year-old St. Paul resident, rode over to Walz's residence on his bike with his kids shortly after the announcement to deliver their congratulations.

“He’s just down to earth. He gets it. He can talk to anybody,” Ivory said. “He doesn't seem like he's above anybody.”

As governor, Walz had to find ways to work in his first term with a legislature split between a Democratic-controlled House and a Republican-led Senate. Minnesota has a history of divided government, though, and the arrangement was surprisingly productive in his first year.

Walz easily won reelection in 2022, and Democrats flipped the Senate to win full control of both chambers and the governor's office for the first time in eight years. A big reason was the Dobbs decision from the conservative-majority Supreme Court that overturned a federal right to an abortion.

Walz currently serves as co-chair of the bipartisan Council of Governors, advising the president and the Cabinet on homeland security and national defense issues. He was first appointed to the position by Trump, then later reappointed by Biden.