Hosted by CBS News, the event gave the pair the chance to introduce themselves and go on the attack against the opposing ticket.

Each man pointed to the crises of the day as reasons for voters to choose their respective running mates for president.

Mr Walz, a two-term Democratic governor of Minnesota, used a question on whether he would support a pre-emptive strike on Iran to paint Donald Trump as too dangerous for the country and the world in an unstable moment.

"What's fundamental here is that steady leadership is going to matter," said Mr Walz.

"And the world saw it on that debate stage a few weeks ago, a nearly 80-year-old Donald Trump talking about crowd sizes is not what we need in this moment."

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Trump 'a deterrent'

Mr Vance, in his reply, argued that Mr Trump is an intimidating figure whose presence on the international stage is its own deterrent.

"Donald Trump actually delivered stability," the Republican freshman senator from Ohio said.

Toward the end of the 90-minute debate, Mr Walz demanded Mr Vance agree to abide by the results of the election and commit to a peaceful transfer of power.

When Mr Vance was asked by the 60-year-old Democrat if Mr Trump lost the 2020 election, however, he replied: "Tim, I'm focused on the future."

"That is a damning non-answer," Walz shot back. "I'm pretty shocked by this. He lost the election. This is not a debate, it's not anything anywhere other than in Donald Trump's world."

Republican nominees 'villainise legal immigrants'

Mr Walz also accused Mr Vance and Mr Trump of villainising legal immigrants in Mr Vance's home state, pointing to Republican Ohio governor Mike DeWine.

The midwestern governor had to send in extra law enforcement to provide security to the city's schools after Mr Vance tweeted about - and Mr Trump amplified false claims about - Haitians eating pets.

"This is what happens when you don't want to solve it, you demonise it," Mr Walz said.

Mr Vance said the 15,000 Haitians in the city had caused housing, economic and other issues that the Biden-Harris administration was ignoring.

When the debate moderators pointed out that the Haitians living there had legal status, Mr Vance protested that CBS News had said its moderators would not be fact-checking, leaving the onus to the candidates.

As Mr Vance continued and the moderators tried to move on, his microphone was cut and neither man could be heard.

'I'm a knucklehead at times' - Walz

Mr Walz was asked about a report this week that he was not in China during the violent 1989 Tiananmen Square crackdown, as he had previously claimed.

"I'm a knucklehead at times," he said. "I got there that summer and misspoke on this.

"So I was in Hong Kong and China during the democracy protests, and from that, I learned a lot about what it means to be in governance."

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'I was wrong about Trump' - Vance

Mr Vance, meanwhile, defended his running mate despite having criticised Mr Trump ahead of the 2016 election.

"I was wrong about Donald Trump," he said. "I was wrong, first of all, because I believed some of the media stories that turned out to be dishonest fabrications of his record.

"But most importantly, Donald Trump delivered for the American people."

The pair struck a noticeably friendlier tone than the matchup between Mr Trump and Ms Harris, which some analysts say the incumbent vice president won, and which left the Republican candidate needing to hold a news conference immediately afterwards.