AMNA NAWAZ: Welcome to the "News Hour."

The contenders for this November's presidential race are officially set.

GEOFF BENNETT: Minnesota Governor Tim Walz is joining Democratic presidential nominee Kamala Harris as her running mate this November.

And he's joining her on stage tonight at a rally in Philadelphia.

AMNA NAWAZ: Walz is a familiar face in Minnesota and the halls of power in Washington, D.C., but a relative newcomer to the national stage.

Along a white picket fence in St. Paul, Minnesota today, a crowd gathers to send off Governor Tim Walz after getting the call from presidential nominee Kamala Harris to join the Democratic ticket.

KAMALA HARRIS, Vice President of the United States (D) and U.S. Presidential Candidate: Listen, I want you to do this with me.

GOV.

TIM WALZ (D-MN), Vice Presidential Candidate: I would be honored, Madam Vice President.

AMNA NAWAZ: The duo is up against the Republican ticket of former President Donald Trump and Ohio Senator J.D.

Vance, who went after his newly named counterpart at a Philadelphia rally today.

SEN. J.D.

VANCE (R-OH), Vice Presidential Candidate: Tim Walz's record is a joke.

He's been one of the most far left radicals in the entire United States government at any level.

(CHEERING) (APPLAUSE) SEN. J.D.

VANCE: The reason I didn't say a whole lot about Tim Walz is because the Democrats have showed a willingness to pull a little switcheroo on us.

So I don't even know if we're actually going to get Tim Walz out of this campaign.

AMNA NAWAZ: Walz, a 60-year-old father of two, is currently in his second term as Minnesota governor, with a 54 percent state approval rating in a July Morning Consult survey and a reputation for a relatable, some say, folksy approach.

HOPE WALZ, Daughter of Tim Walz: I think we're going to go do the slingshot.

GOV.

TIM WALZ: Which I don't know what it is, and they're keeping it from me.

AMNA NAWAZ: And though he's racked up a substantial political record over nearly two decades in public office, Walz hasn't been very well-known outside his home state.

HOPE WALZ: Good job, dad.

GOV.

TIM WALZ: Oh, thanks, Hope.

AMNA NAWAZ: In 2020, that began to change.

GOV.

TIM WALZ: Generations of pain is manifesting itself in front of the world.

And the world is watching.

AMNA NAWAZ: After a police officer murdered George Floyd in Minneapolis, Walz condemned the killing, and, days later, after some protests turned violent, called in the National Guard to respond to rioters.

GOV.

TIM WALZ: Everything that we believe in, these people are trying to destroy.

So, if you are on the streets tonight, it is very clear, you are not with us.

You do not share our values.

And we will use the full strength of goodness and righteousness to make sure that this ends.

AMNA NAWAZ: The right criticized his response as slow, and Walz himself later acknowledged the -- quote -- "abject failure" of that response.

In 2023, after his party won control of the Minnesota House and Senate, Walz signed into law a laundry list of Democratic priorities, providing free meals to K-12 students, the largest child tax credit in the country, enshrining abortion rights into state law, increasing LGBTQ protections, legalizing marijuana, and granting voting rights to ex-offenders.

His selection by Harris is seen by some as a nod to the party's progressive wing.

JAKE TAPPER, CNN Host: Do you think your record is an asset to the ticket, or would it risk fueling Trump's attacks as you being a big government liberal?

GOV.

TIM WALZ: What a monster.

Kids are eating -- eating and having full bellies so they can go learn.

And women are making their own health care decisions.

And we're a top five business state and we also rank in the top three of happiness.

AMNA NAWAZ: But earlier in his career on Capitol Hill, he was known as a moderate.

GOV.

TIM WALZ: I intend to come here to Washington to provide authentic leadership.

AMNA NAWAZ: In 2006, he flipped his Minnesota U.S. House seat from red to blue, becoming the highest-ranking enlisted veteran ever in Congress.

Over six terms and a dozen years, he ranked among the most bipartisan lawmakers, supported ongoing operations in Iraq, while opposing more boots on the ground, pushed for a minimum wage hike and prescription drug cost negotiations, voted against President Obama's 2009 Wall Street bailout plan, but backed the Affordable Care Act.

Before entering politics, Walz served 24 years with the Army National Guard, enlisting at the age of 17, alongside his day job teaching high school social studies and coaching football.

In recent weeks leading up to his selection, Walz made a name for himself as a willing warrior for Harris.

Are you what this ticket needs to be able to beat the Trump/Vance ticket?

GOV.

TIM WALZ: Well, I don't know about that, Amna.

What I can tell you is, is that we will beat that ticket.

This chaos that Donald Trump brings, this dystopian view of America, Kamala Harris' joy, you can feel it.

AMNA NAWAZ: Going viral by branding the opposing ticket in this way.

GOV.

TIM WALZ: Well, it's true.

These guys are just weird.

AMNA NAWAZ: The Harris/Walz campaign will spend the next week touring swing states, with stops in Pennsylvania, Wisconsin, Michigan, North Carolina, Arizona, and Nevada, as it introduces the country to a new national political player and potential future vice president.

One of the biggest challenges for the Harris/Walz campaign will be introducing Governor Walz to the American people.

Our new PBS/NPR/Marist poll out today shows that 71 percent of Americans don't know who he is.

For more on the Minnesota governor, I'm joined now by Twin Cities PBS reporter Mary Lahammer.

She's been following Walz's career for some 20 years.

Mary, good to see you.

Thanks for joining us.

MARY LAHAMMER, Twin Cities PBS: Thank you.

AMNA NAWAZ: So you were outside his home earlier today as the news broke.

Tell me a little bit about what you heard from people out there.

MARY LAHAMMER: Yes, it was an interesting environment.

An organic crowd developed.

There were folks walking their dogs out on a morning run, a walk, and decided to stay, and they actually got to see him depart in the motorcade, and just started cheering for him out of the blue.

And then talking to them afterwards, they're excited.

Minnesotans like to play an outsized role in national politics.

They're kind of proud of it.

I think people are learning the statistic that if Walz wins three out of the last six Democratic vice presidents will be from Minnesota.

But as your poll shows, he's got to introduce himself to the nation.

AMNA NAWAZ: He does have an uphill battle there.

The vast majority of Americans don't know who he is or don't know what to think of him.

So the campaign, as we know, is already working to set that narrative with videos like this they released today.

GOV.

TIM WALZ: I coached football and taught social studies for 20 years.

And I tried to teach my students what small-town Nebraska taught me, respect, compromise, service to country.

And so when I went into government, that's what I carried with me.

AMNA NAWAZ: So, Mary, you have covered him for some 20 years.

What's the headline here for what people need to know about who is Tim Walz?

MARY LAHAMMER: Yes, I will go back to his very first run for office.

And I remember some trusted sources saying you got to get down to this rural Republican district where this football coach is actually making a race of it and eventually flipped the seat.

I went back and studied that debate and tried to kind of ascertain how much he has changed.

And it was interesting to me to see that he is still kind of -- was the fearless, self-effacing, but aggressive, quick kind of his feet.

So he's been able to debate and really pivot for a long time, but introducing himself to a national audience will be new.

He's used to the Minnesota press corps.

He's done a lot of national news, and was even surprised.

In our recent interview, we discussed how that Republicans are weird phrase, how we kind of coined that phrase.

And he was almost embarrassed, saying, oh, gosh, shucks.

I wasn't trying to be mean about it.

So we will see how those Midwestern tendencies go on the national stage.

AMNA NAWAZ: So, Mary, some folks are hailing his selection here as a nod to progressives of the Democratic Party.

But I had a Dem source tell me earlier today that he's actually much more moderate than many in the media make him out to be.

What do you make of that?

MARY LAHAMMER: It depends which office you're talking about.

When he was a member of Congress from a rural previously Republican district, he was much more of a moderate.

Then, when he became governor for the state and his lieutenant governor, Peggy Flanagan, definitely took him in more of a progressive stance.

And then he got an all-Democratic legislature, so ended up passing just a very large list of highly progressive items.

So, some folks say, was it a bait-and-switch?

He originally ran on this concept of one Minnesota.

We are still probably rather divided here.

AMNA NAWAZ: Well, he is relatively popular at the state level, right?

He has a 54 percent approval rating in Minnesota.

What do his critics there say about him?

And could any of those become vulnerabilities on the national stage?

MARY LAHAMMER: Yes, a good portion of his time in office as governor has been in front of a divided legislature.

He recently had the all-Democratic trifecta.

But before that, he had a lot of critics, and he had a hard road in divided government.

Minnesota is a state, four Democrats, four Republicans in Congress.

We're slightly purple.

And folks here are very critical of his time during the pandemic in particular.

We had a lot of lockdowns.

Of course, we had the riots following George Floyd's murder and were very critical of him being slow to send the National Guard out.

Also, during the pandemic, we had the largest fraud in the Feeding Our Future fraud case.

I think the governor will probably be talking about the fact that those cases have been brought to justice, and there have been convictions in both of those instances.

AMNA NAWAZ: Big week for Minnesota.

We know you will be covering his career moving forward as well.

That is Mary Lahammer of Twin Cities PBS joining us tonight.

Mary, thank you.

Good to see you.

MARY LAHAMMER: Thank you.