Seven things to know about the US vice presidential debate

Analysis - Vice-presidential debates are the under-card of US election discussions.

Except, with Donald Trump and Kamala Harris running so close in the presidential elections, every debate could have significance.

So, it was when Minnesota Governor Tim Walz, Harris' running mate, met Ohio Senator JD Vance, Trump's pick, this afternoon in a surprisingly cordial debate, focused mainly on the issues, but one which also revealed differences between the two camps.

Here's seven things to know.

Policy debate

This was a debate where policy issues were at the heart of the debate. Certainly, there were pre-prepared talking points with JD Vance focusing on Vice President Kamala Harris' years in the White House and Tim Walz pointing back to Trump's presidency, and occasionally candidates sliding past a question.

But largely this was a debate of substance where Vance and Walz set out contrasting views on what they would do in power - and occasionally even discussed how they agreed with each other. At a time when the US is categorised as terminally divided, this was largely a debate of the issues.

Immigration, housing, abortions and gun policy took up most of the time.

"I've enjoyed this debate," said Walz towards the end.

But there was one area where the two were miles apart:

Who won the 2020 election?

This may have been the high point for Walz, though coming at the end when many in the audience may have switched off.

The question was whether Trump was a threat to democracy after his actions after losing the 2020 election and during the 6 January, 2021 Capitol riots.

Vance said that he was focused on the future, not categorising the past. He accused Kamala Harris of misdemeanours. "Kamala Harris is engaged in censorship at an industrial scale," he told the moderators.

"It's really rich for Democratic leaders to say that Donald Trump is a unique threat of democracy when he peacefully gave over power on January the 20th."

Walz countered that January 6 violence, which included a march on the governor's mansion in Minnesota where Walz was working, was in a different league to questioning posts on social media.

"To deny what happened on January 6, the first time an American president or anyone tried to overturn an election" was serious and unacceptable, he said. "This has got to stop. It's tearing our country apart."

Walz's son witnessed a shooting

The candidates had one of their most personal moments when talk turned to gun laws.

Vance had spoken about making American schools more secure. "We have to make the doors lock better. We have to make the doors stronger ... The idea that we can magically wave a wand and take guns out of the hands of bad guys, it just doesn't fit with recent experience."

The Democrat replied that the conversation was a good start but more had to be done.

Walz said he had sat with families who had lost children in the shootings at Sandy Hook Elementary School in 2012.

Then Walz revealed his son had witnessed a shooting at a community centre while there to play volleyball. "It breaks your heart," he said.

Vance offered his sympathies.

"I didn't know that your 17-year-old witnessed a shooting. I'm sorry about that - Christ have mercy. It is awful."

Listen carefully

This was a very different debate to Trump-Harris. Then, Trump barely looked at his competitor. Harris did look at Trump, a lot; her head often cocked on one side, her hand on her chin and a quizzical look on her face.

This was different. Both looked at each other, they seemed to listen. There were fewer times when one mugged and when it happened, it was usually Vance who broke the "third wall" to look out intently at the television audience. Otherwise, these were candidates working hard to be seen to be listening hard.

The Off-screen bosses

Like all vice-president debates it was the unseen presence of their running mates who cast shadows. To Vance, Harris was an incumbent who had to bear responsibility for the failure to stem illegal immigrants at the border. Conversely, Trump led an administration which had kept America strong during Covid-19 and stood up to China.

Naturally, for Walz it was the opposite. Trump was a democracy-challenged president with no scruples about endangering democracy. And Biden and Harris had delivered a strong record of economic prosperity.

When you are a vice-presidential candidate, it is the boss that matters.

Mics off

Amidst all the words, there was one moment of silence, or at least the muted sound of people talking off-stage. CBS had threatened to mute mics and 30 minutes into the debate it did. The flashpoint came when moderator Margaret Brennan pointed out that a number of Haitian immigrants in Springfield, Ohio were in the country legally.

Springfield had been in the spotlight. Illegal immigration had been in the spotlight and Trump's debate pronouncement that illegal immigrants "were eating the dogs, they're eating the pets" was in the air.

Vance said the city and its hospitals, schools and housing market were being overwhelmed by immigrants. In turn, Walz said the Trump team were demonising decent people. And so, the debate circled round and round on Springfield until Brennan stopped the debate and made her fact-check on the legality of Haitian immigrants.

Except Vance would not stop. He objected to her assertion and then leaned into a discussion of immigration law. Brennan kept trying to cut him off as Walz then joined in.

When Vance kept speaking, CBS cut the mics. For a few seconds the only noise was the echoes of the two men in the cavernous theatre still speaking - but off-mic.

"Gentlemen, the audience can't hear you because your mics are cut," Brennan explained.

Those uncomfortable moments

Both Vance and Walz were well-prepped, and spoke sincerely about their views, their families and experiences

There were the moments of discomfort. There was one which appeared as a sideshow, though it may shed light on a candidate's character. It was the moment Walz's voice trailed off into silence as he tried to explain whether he had actually been in Hong Kong and China to witness the Tiananmen protests in the spring and early summer of 1989. He probably wasn't.

"I got there that summer and misspoke," he told the audience. He said he was a "knucklehead" at times.

"Many times, I will talk a lot, I will get caught up in the rhetoric, but being there, the impact it made, the difference it made in my life, I learned a lot about China," Walz said.

He ended "I misspoke on this". The camera lingered on him as the silence lengthened into discomfort.

Vance on the other hand was well-practiced on why he had once called Trump an "idiot" and his policies "reprehensible". He knew the question would come; it came. He said he had done a lot of media interviews to explain.

"I was wrong about Donald Trump," he said looking down the camera.