AMNA NAWAZ: Welcome to the "News Hour."

A debate has been set between former President Trump and Vice President Harris.

ABC News says it will host the two candidates in a head-to-head matchup on September 10.

GEOFF BENNETT: That news came as the presidential hopefuls and their running mates continued on the campaign trail today from a Michigan union hall to the gilded halls of Mar-a-Lago.

DONALD TRUMP, Former President of the United States (R) and Current U.S. Presidential Candidate: Well, thank you very much.

GEOFF BENNETT: Donald Trump today held his first major campaign event since Vice President Kamala Harris announced her pick of Minnesota Governor Tim Walz as her running mate.

DONALD TRUMP: There's certainly never been anybody so liberal like these two.

GEOFF BENNETT: For nearly 10 minutes, the former president ticked through a litany of now-familiar grievances and unfounded and false claims, taking particular issue with the reporter's question about the Harris campaign's crowd sizes.

DONALD TRUMP: I have 10 times, 20 times, 30 times the crowd size.

GEOFF BENNETT: He compared the crowd size of his Ellipse speech on January 6 to that of Dr. Martin Luther King Jr.'s famous "I Have a Dream" speech and when asked why he's been off the campaign trail for days, offered this: DONALD TRUMP: Because I'm leading by a lot and because I'm letting their convention go through.

And I am campaigning a lot.

I'm doing tremendous amounts of taping here.

We have commercials that are at a level I don't think that anybody's ever done before.

Plus, in certain cases, I see many of you in the room where I'm speaking to you on phones, I'm speaking to radio, I'm speaking to television, television's coming over here.

Excuse me, what are we doing right now?

She's not doing any news conference.

You know why she's not doing it?

Because she can't do a news conference.

She doesn't know how to do a news conference.

She's not smart enough to do a news conference.

GEOFF BENNETT: Trump, who previously backed out of a presidential debate with Harris, today proposed three new dates for debates, including one with ABC News, to which Harris already committed.

Trump today was decidedly less on message than his own running mate, J.D.

Vance, who took aim at Walz's military service, reminiscent of the 2004 Republican effort to discredit the war record of then-Democratic presidential nominee John Kerry, a tactic orchestrated by Trump's now campaign adviser Chris LaCivita.

Vance at his campaign event yesterday used the controversial term stolen valor, often used to describe people who've lied outright about serving in the military.

SEN. J.D.

VANCE (R-OH), Vice Presidential Candidate: When the United States of America asked me to go to Iraq to serve my country, I did it.

When Tim Walz was asked by his country to go to Iraq, you know what he did?

He dropped out of the Army and allowed his unit to go without him.

GEOFF BENNETT: There is no evidence that Walz retired to avoid a wartime deployment.

And it's a line of attack that may not work.

Walz has faced similar attacks from Republicans before and during his successful campaigns for Congress and governor.

GOV.

TIM WALZ (D-MN), Vice Presidential Candidate: This guy doesn't know the first thing about unity or service.

And his running mate is just as dangerous and backward as he is.

GEOFF BENNETT: At a United Auto Workers event in Detroit today, Harris and Walz pushed back on the Trump campaign's attacks.

KAMALA HARRIS, Vice President of the United States (D) and U.S. Presidential Candidate: We believe in each other.

We believe in the collective.

We're not falling for these folks who are trying to divide us, trying to separate us.

So, Michigan, I ask you, are you ready to make your voices heard?

(CHEERING) (APPLAUSE) GEOFF BENNETT: Their Michigan event today follows a campaign rally last night outside Detroit that was moved to an airplane hangar to accommodate a crowd of nearly 15,000 people, according to the Harris campaign.

KAMALA HARRIS: This election is going to be a fight.

(CHEERING) (APPLAUSE) KAMALA HARRIS: We like a good fight.

(CHEERING) (APPLAUSE) KAMALA HARRIS: When you know what you stand for, you know what to fight for.

We know what we stand for.

(CHEERING) (APPLAUSE) GEOFF BENNETT: As Harris emphasized, a message of unity, a familiar divide, a small group of protesters chanting what appeared to be a pro-Palestinian message, interrupting Harris' speech.

Harris spoke with the leaders of the Uncommitted National Movement before her rally and acknowledged the protesters at first.

KAMALA HARRIS: I'm here because we believe in democracy.

Everyone's voice matters, but I am speaking now.

GEOFF BENNETT: But her patience ran thin after repeated interruptions.

KAMALA HARRIS: You know what?

But if you want Donald Trump to win, then say that.

Otherwise, I'm speaking.

(CHEERING) (APPLAUSE) GEOFF BENNETT: As the Harris campaign continues its battleground blitz, it's out today with a new ad campaign tailored to Latino voters, emphasizing Harris' background, raised by an immigrant mother.

After Michigan, Harris heads next to make the case to voters in Arizona and Nevada.

As the two newly cemented tickets continue to make their case to voters, the recent shakeups in the race have led to a reshuffling of the electoral math needed to win.

The Cook Political Report is out with updated ratings for the presidential race, moving the three battleground states of Arizona, Georgia and Nevada, from lean Republican to toss-up.