(NewsNation) — Democratic presidential nominee Kamala Harris selected Minnesota Gov. Tim Walz as her running mate in the 2024 election, the current vice president announced Tuesday.

“I am proud to announce that I’ve asked @walzforgovernor to be my running mate,” Harris posted to Instagram. “One of the things that stood out to me about Tim is how his convictions on fighting for middle-class families run deep. It’s personal.”

“We are going to build a great partnership. We are going to build a great team. We are going to win this election,” she continued.

Walz responded to Harris’ selection by saying it was the “honor of a lifetime” to join her campaign.

Harris and Walz made their first appearance together as the Democratic ticket in Philadelphia.

The Temple University arena in Philadelphia was packed, with every one of about 10,000 seats taken.

Pennsylvania Gov. Josh Shapiro and Sens. John Fetterman and Bob Casey spoke before Harris and Walz took the stage.

Speaking just two weeks after launching her presidential campaign, Harris called her and Walz “underdogs.”

“But we have the momentum,” she said.

Harris said Walz is a “fighter for the middle class” and a “patriot who believes in the promise of America.”

The Harris campaign said it had raised more than $20 million since Tuesday morning’s announcement of Walz as the vice president’s running mate.

Among a list of accomplishments, Harris nodded to Walz’s representation of a purple congressional district and a distinction he earned while in Congress.

She said, “He was the highest-ranking enlisted man to ever serve in the United States Congress and the top Democrat on the Veterans Committee.”

In his first speech as presumptive vice presidential nominee, Walz thanked Harris for her invitation to join the ticket.

“Thank you for the trust you have put in me,” Walz said to Harris. “Thank you for bringing back the joy. I am thrilled to be on this journey with you and Doug.”

“Donald Trump sees the world a little differently than us,” Walz said. “First of all, he doesn’t know the first thing about service; he doesn’t have time for it because he’s too busy serving himself.”

“Trump weakens our economy to strengthen his own hand,” he continued. “He froze in the face of the COVID crisis. He drove our economy into the ground.

“Make no mistake, violent crime was up under Donald Trump, and that’s not even counting the crimes he committed,” Walz said.

Walz attacked Sen. JD Vance, saying, “I can’t wait to debate the guy.”

“JD Vance literally wrote the foreword for the Project 2025 agenda,” Walz said. “Like all regular people I grew up with in the heartland, JD studied at Yale, had his career funded by Silicon Valley billionaires and then wrote a bestseller trashing that community. C’mon. That’s not what Middle America is.”

“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. So, let’s get this done, folks! Join us,” Walz earlier posted to X.

In another post, he promised to fight for the common good.

The selection comes as Harris crossed a largely ceremonial and important milestone late Monday night: She officially won enough votes during a virtual roll call of delegates to become the Democratic Party’s presidential nominee.

She took more than 99% of the vote.

A source familiar with the campaign told NewsNation Walz would be given a Secret Service protective detail once he lands in Philadelphia.

Harris-Walz ticket

Prominent Democratic elected officials, party leaders and political organizations quickly lined up behind Harris in the days after President Joe Biden’s exit from the race. Her campaign set a new 24-hour record for presidential donations after Biden’s announcement and exceeded $200 million raised in her first week despite Harris not yet being officially declared the Democrats’ nominee.

Walz began being mentioned as a contender for the spot at the end of July, with Democrats applauding his affable persona, praise among unions and national experience as chair of the Democratic Governors Association. 

Walz’s liberal policy record and decorated background as a congressman and soldier made him stand out as a vice presidential contender.

Walz won his congressional bid in 2006 and served for 12 years before pivoting his career in 2019 to assume the governorship. In that time, he gained recognition as a top Democrat on the House Veterans’ Affairs Committee and the highest-ranking enlisted soldier in congressional history.

After the news that Biden dropped out of the presidential election, Walz threw his full support behind Harris.

“I’m proud to give Kamala my full support and commit to doing everything in my power to make sure she gets elected in November,” Walz posted on X.

Harris doesn’t have much of a relationship with Midwest voters, something that Walz could help her campaign secure as her running mate this November.

Axios reported Walz would add to Harris’ campaign a consistent progressive voice that could help secure white working-class support in Midwestern states.

“In terms of auditioning, (Walz is) doing an exceptional job,” a person familiar with the Harris campaign’s VP conversations told Politico. “He’s got the Midwest grit, the Midwest sensibility and that appeal goes beyond the Midwest.”

Shapiro, who was another top contender to be picked as Harris’ running mate, posted to social media, pledging his support to Harris and Walz over the next 90 days ahead of the election.

“Over the next 90 days, I look forward to traveling all across the Commonwealth to unite Pennsylvanians behind my friends Kamala Harris and Tim Walz and defeat Donald Trump. See you tonight in Philly,” Shapiro wrote on X.

Tim Walz’s relationship with Harris

Prior to the announcement, Harris’ circle was reportedly weighing how well the vice president would mesh with Walz, especially since he has been known to be a bit gruff during his congressional years.

Walz has since been out on the campaign trail for Harris, promoting the vice president and saying he will do whatever it takes to get her elected in November.

Appealing to Democratic voters helped Walz earn his spot as Harris’ running mate, especially after his comments regarding former President Donald Trump and his running mate, Ohio Sen. JD Vance.

“These guys are just weird,” Walz said in an MSNBC interview. “They’re running for He-Man women-haters club or something.”

Walz also posted to X, poking fun at Trump’s recent campaign visit to his state.

“Donald Trump is coming back to the State of Hockey tomorrow for the hat trick,” Walz wrote. “He lost Minnesota in ’16, ’20, and he’ll lose it again in ’24.”

Walz will oppose Vance on the GOP side, at least indirectly if not at a debate, which has not yet been scheduled.

Harris-Walz campaign hits the road

According to a campaign statement, Harris and Walz will hit seven cities in five days beginning Tuesday: Philadelphia; Eau Claire, Wisconsin; Detroit; Durham, North Carolina; Savannah, Georgia; Phoenix and Las Vegas.

The itinerary will include big arena and college campus rallies as well as “more intimate settings” like union halls, restaurants and campaign field offices.

“These stops will highlight the ticket’s strength in the Blue Wall and Sunbelt, from urban areas to rural communities. At each stop, our new ticket will be joined by local elected officials, union members, faith leaders, and more,” the Harris campaign said.

Trump-Vance campaign reacts to Walz

Karoline Leavitt, the press secretary for Trump’s campaign, released a statement after Harris’ selection of Walz.

“If Walz won’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,” she said.

Vance reacted to the news as well, posting to his campaign website.

“Bring. It. On,” Vance said. “President Trump and I will save America this November, whoever’s on the Democrat ticket.”

Lawmakers react to Harris’ VP pick

As news of Harris’ pick spread, lawmakers from both sides of the aisle reacted on social media.

“Vice President Harris made an excellent decision in Gov. Walz as her running mate. Together, they will govern effectively, inclusively, and boldly for the American people,” Rep. Alexandria Ocasio-Cortez, D-N.Y., posted to X.

“Walz was a good choice. He had me at ‘Free breakfast and lunch for every child at school,'” former presidential candidate Marianne Williamson posted to X. “By the way, that will improve the educational performance of those children and ultimately their ability to create wealth and opportunity for themselves.”

But while Democrats praised the decision, many Republicans were fast to criticize Walz.

“Democrats doubling down on the Progressive movement. Harris/Waltz is a win for open borders, socialism, and Iran,” Nikki Haley, former U.N. ambassador and South Carolina governor, said.

“Tim Walz is a perfect choice for Kamala Harris. He let BLM rioters, arsonists, and looters rampage through his state and she encouraged donations to the bail fund for the few who were arrested,” Sen. Tom Cotton, R-Ark., posted to X.

Even Biden chimed in on Harris’ pick: “The first major decision a party nominee makes is their choice for Vice President. And Kamala Harris has made a great decision in choosing Governor Tim Walz to be her running mate.

Passing the torch

Worries over Biden’s fitness for office were replaced by fresh signs of unity after a seismic shift to the presidential contest that upended both major political parties’ carefully honed plans for the 2024 race.

The campaign also saw a surge of interest after Harris launched her candidacy, with more than 28,000 new volunteers registered since the announcement — a rate more than 100 times an average day from the previous Biden reelection campaign, underscoring the enthusiasm behind Harris.

Some early polling has shown signs of optimism for Harris and Democrats. Surveys have suggested Harris is making some gains against Trump in key states compared to Biden.

Plus, a new poll reflected an increase in her favorability rating among Americans. In the ABC News/Ipsos poll released Sunday, 43% of Americans say they have a favorable view of Harris — an eight-point jump from last week’s 35% favorability rating.

The Democratic National Committee expects Harris to head to the party’s convention Aug. 19 in Chicago — setting up for a lively next month for Democrats.

NewsNation’s Kevin Bohn and Sean Noone contributed to this report.