Prime Minister Malcolm Turnbull and Opposition Leader Bill Shorten need to convince these voters to choose them. Picture: Lyndon Mechielsen/News Corp

A group of 30 uncommitted voters from those electorates will make up the audience for news.com.au’s leaders’ debate on Facebook Live this Friday at 6pm.

These Australians, picked by the independently owned Galaxy Research, will be asking Malcolm Turnbull and Bill Shorten whatever questions that could influence their vote.

So they are the questions that could decide the election.

The 21 marginal seats held by the Liberals include the most at-risk — Lyons, Petrie and Hindmarsh — as well as the bellwether seat of Eden-Monaro, whose result has historically reflected the overall outcome of elections.

The Opposition needs to take around 20 seats in order to have a majority government. While it could take other seats, these should be the easiest. If it fails to take any of these seats, the task will get increasingly hard.

Galaxy founder David Briggs said the audience would be a mixture of men and women of different ages from the seats that count, who identify themselves in telephone surveys as having not yet made up their mind on how to vote.

“They will be advised they can ask anything that will help them make up their mind,” he said. “We don’t know what the important issues will be. We know from Newspoll it does come back to key issues of health, education and the economy.

Voters and their families in Yass in the bellwether federal seat of Eden-Monaro in southern NSW. Picture: Ray StrangeSource:News Corp Australia

“The Government is campaigning on the economy and jobs and Labor is going for its strong suit, health and education.”

He said other issues, such as asylum seekers, were pushed down the list of importance. The Coalition has a certain track record and Mr Shorten has said under Labor there would be no change. “He’s trying to take the issue off the table,” added Mr Briggs.

Many of these seats represented at the debate are ones that swung from Labor to Liberal when Tony Abbot won the 2013 election, making significant gains in Western Sydney, for example.

So the Opposition will be aiming to win back traditionally Labor-held seats, with NSW over-represented because the Liberals did so well there at the last election.

While you would expect these seats to swing left, this will partly depend on the performance of local MPs.

“Most of these seats will have Liberal members going to election for the first time as a sitting member,” said Mr Briggs.

“In the three years since the election they will have built a profile, and consequently they tend to suffer a swing less pronounced than the national average.

“Labor really have to get the national swing we’ve been seeing in Newspoll.”

At the moment, the opposition isn't quite there.

So Friday’s debate could be crucial for this election result.

THE GALAXY RESEARCH SEATS THAT COUNT

Banks, Lindsay, Macarthur, Reid, Eden-Monaro, Gilmore, Page, Robertson, Deakin, La Trobe,

Corangamite, Lyons, Braddon, Bonner, Petrie, Hindmarsh.

Submit your debate questions here.