The men who want to be America's vice-president are preparing for their first, and probably only, televised campaign debate.

It's another important moment in the US election race, which polls suggest is still an incredibly close contest. Tim Walz and JD Vance are both relatively low-profile politicians who haven't spent much time on the national stage – so a lot of voters don't know too much about them. 

The debate is being hosted by CBS News at the network's broadcast centre in New York City.

Who are the candidates for vice-president?

On the Democrats side, Kamala Harris's running mate is Tim Walz, a former high school teacher and American football coach. 

Walz, 60, was first elected to the national Congress in 2006, representing a rural district in Minnesota. He quit Congress in 2019 to become the state's governor. 

For the Republicans, Donald Trump's vice-presidential nominee is JD Vance, the author of Hillbilly Elegy, a best-selling memoir about life in poverty-stricken rural Ohio. 

Vance, 40, was elected to the US Senate in 2022, after serving in the US Marine Corps and working as a venture capitalist.

What time is the vice-presidential debate?

The debate will start at 9pm Tuesday, local time, which is 11am Wednesday, AEST.

How can I watch the vice-presidential debate?

In Australia, you can watch the debate on the ABC News Channel. 

We'll also be live blogging the debate here on the ABC News website.

American host broadcaster CBS will also stream the debate on its website and YouTube channel. 

What are the rules for the vice-presidential debate?

The rules, agreed to by both campaigns, are similar to the previous presidential debates.

• The debate will run for 90 minutes, with two commercial breaks of 4 minutes.

• CBS journalists Norah O'Donnell and Margaret Brennan will ask the questions and moderate the debate.

• After being asked a question, the candidate will get 2 minutes to answer, and their opponent will then get 2 minutes to respond. Each candidate will then get a minute for further rebuttals. At the moderators' discretion, the candidates may get an extra minute each to continue the discussion.

• Candidates will not be told questions or topics in advance.

• There will be no audience.

• No props are allowed.

• No pre-written notes are allowed, but candidates will be given a pen and paper.

Something that proved controversial in the previous presidential debates was the decision to mute candidates' microphones when it wasn't their turn to speak. In this debate, CBS says it "reserves the right" to mute microphones, but they could remain hot throughout. So there could be more back-and-forth discussion, or messy interjection, in this debate than the presidential ones.

Six things to look out for:

'Midwest dad' vibes

Both Walz and Vance were chosen to be VP candidates, at least in part, to appeal to certain voting demographics. 

Both men have talked up their backstories of rising from humble beginnings, and leaned into "Midwest dad" personas. 

Their respective campaigns hope they will resonate in middle America, far from Harris's progressive home state of California and Trump's worlds of Manhattan real estate and Florida luxury resort life.

But each will paint the other as extremist. Vance has called Walz "one of the most far-left radicals in the entire United States government at any level". Walz is known for critiquing Vance and Trump as "weird" and "creepy as hell".

Questions about Walz's military history

Both Vance and Walz have served in the military, but neither in combat. 

Vance served four years in the US Marine Corps, which included about six months in Iraq in 2005 as a military journalist.

Walz served 24 years in the National Guard — part of the US Army reserve — but he retired in May 2005. This was three months after he'd applied to run for Congress, and two months after his artillery unit was told it might be deployed to Iraq.

This has become one of the things Vance most commonly attacks Walz on. He has described Walz's decision to retire just before possible deployment as "shameful". 

He's also criticised Walz over a 2018 video, which was shared by the Harris campaign, showing Walz saying he'd carried weapons "in war". 

The Harris campaign later said Walz "misspoke" when he said he carried weapons in war. Vance has accused Walz of "stolen valour".

Vance's views on Project 2025

A key plank of the Democratic Party strategy has been linking Trump and Vance to the controversial Project 2025. Put together by the conservative Heritage Foundation, the "presidential transition project" contains contentious policies like banning abortion, eliminating climate change programs and disbanding the Department of Education. It also proposes stacking the civil service with loyalists and expanding the president's power.

While some of Trump's allies and former staff helped write the plan, Trump has insisted he has "nothing to do with it". But Vance is close with the Heritage Foundation's president, Kevin Roberts, and even wrote the foreword for his upcoming book, noting that "in the fights that lay ahead, these ideas are an essential weapon".

Those claims about cats

The most talked about moment from the most recent debate, between Trump and Harris, was Trump's claim that Haitian migrants were "eating the pets" in the town of Springfield, Ohio. 

City and state officials, including Ohio's Republican governor, maintain there's no evidence of this. Shortly after the debate, Vance conceded it may be untrue — but he defended the claim anyway, even encouraging social media users to share pet memes.

Vance told CNN he'd been "trying to talk about the problems in Springfield for months", and "if I have to create stories so that the American media actually pays attention to the suffering of the American people, then that's what I'm going to do".

It's not the only pet-related claim that Vance has been forced to defend. His 2021 comments about the Democratic Party being run by "a bunch of childless cat ladies who are miserable at their own lives" attracted a tonne of backlash, including from Taylor Swift, who embraced the label when she endorsed the Harris-Walz ticked after the last debate.

Vance has argued he was being sarcastic, and was trying to make a point about the Democratic Party being "anti-family and anti-child".

Walz's response to riots in Minnesota

Vance regularly attacks Walz over his record in Minnesota, including how he handled riots in its largest city, Minneapolis. The riots, after George Floyd's murder in 2020, caused $US500 million ($723 million) in property damage.

Critics say Walz should have activated the National Guard sooner. Vance said Walz "allowed rioters to burn down Minneapolis". 

Trump, who was then president, praised Walz at the time. Recording from a phone call shows Trump told a group of governors: "I fully agree with the way he [Walz] handled it the last couple of days." Trump's campaign says Trump only praised the governor after he called in the National Guard.

Another approach to fact-checking

During the two presidential debates, we saw two different approaches to fact-checking the candidates. 

In the first, between Trump and President Joe Biden, CNN's moderators did not fact-check the candidates in real-time. But the network's official fact-checkers later found Trump made 30 false claims – far more than Biden.

In the second debate, between Trump and Harris, ABC's moderators did fact-check live. Trump, and many of his supporters, accused the moderators of bias because they pulled him up multiple times and did not catch out Harris. 

CBS says its moderators will not fact-check live – but a QR code on the CBS broadcast will direct viewers to an online fact-checking service.