What's At Stake In The Five By-Election 'Super Saturday'

Both Shorten and Turnbull are sweating on the results to keep their jobs.

Five polls, four states, three seats with a chance to change hands, two leaders sweating on good results to ensure their short-term survival.

One 'super Saturday' of by-elections.

July 28 will see voters head to the ballot box in Braddon (Tasmania), Longman (Queensland), Mayo (South Australia), Perth and Fremantle (both Western Australia). Four by-elections have been forced by the dual citizenship crisis, which claimed the scalps of Labor MPs Justine Keay, Susan Lamb and Josh Wilson, and Centre Alliance representative Rebekha Sharkie; the fifth, in Perth, will come after Labor's Tim Hammond decided to resign for family reasons.

Turnbull on the campaign trail in Longman (AAP Image/Glenn Hunt)

All four (former) dual citizen MPs are recontesting their seats. In a parliament as tight as this one is, numbers-wise, five by-elections in one day could mean major changes in the power balance.

Currently the government only have a one-seat majority in the House of Representatives, and as has been seen recently in losing a few embarrassing, historic votes in the chamber, every vote counts -- so the Coalition would love to pick up a seat or two on super Saturday.

But there's more at stake in the quintet of by-elections than just the short-term. A full federal election is due sometime in the next year, with whispers a good Liberal showing on super Saturday could entice Malcolm Turnbull to bring on a snap election later this year.

A full national poll is due soon, and both major parties are using July 28 to road-test election strategies for the big dance -- Labor pushing messages about healthcare, infrastructure and education, the Liberals talking up jobs, tax cuts and border protection, as well as fine-tuning their "kill Bill" message personally targeting Labor leader Shorten.

But more than that, many will frame the results as a bellwether on both Turnbull and Shorten. If Labor loses any of the four seats they currently hold, the drumbeat will grow louder to consider dumping Shorten, whose personal popularity continues to crater despite Labor's election-winning lead in the national polls; if the Liberals fail to pick up any seats, the mutterings about Turnbull's grasp on the leadership will also increase.

There's a lot riding on these results. Here's what you need to know.

Longman, Queensland

Of the five seats up for grabs, Longman is the one most in play, and the one most heavily contested. Labor's Susan Lamb won the seat by one of the slimmest margins at the 2016 federal election, and following her citizenship fiasco, the Liberals are hoping to pinch the win with their candidate, Trevor 'Big Trev' Ruthenberg.

However, Big Trev has had issues of his own, with a furore over the candidate claiming to have been awarded a medal for his army service that he never won.

Turnbull and the appropriately-named Big Trev. Look at the size of this lad. (AAP Image/Glenn Hunt) NO ARCHIVING

Both sides have been showering money and promises in Longman.

Taking into consideration the likelihood of a decent One Nation vote in the party's Queensland stronghold, with a vigorous campaign mounted by Pauline Hanson, the Liberals would hope preferences from the far-right party would help them over the line.

Queensland has long been seen as the key to winning a federal election, so the Longman by-election represents a test run for strategies ahead of the upcoming national poll. So far, the Longman race has been dominated by talk of border protection, tax cuts, education, hospitals and immigration.

Tip: Liberals to pinch the seat in a very tight race

Braddon, Tasmania

Braddon is the next most-contested seat. The 2016 election saw Labor take the seat with a margin of 53-47, but again following former member Justine Keay's dual citizenship drama, the Liberals would hope they could chip away at that number.

Money and promises have been laid on thick in the Tasmanian seat, with the government announcing submarine test facilities, while Shorten and Turnbull have made multiple appearances in the area.

Shorten and Keay (second left) visit a nursing home in Devonport, Tasmania (AAP Image/Grant Wells)

Both sides are talking up jobs and infrastructure in Braddon, saying people shouldn't have to go to the mainland to get what they need.

Longman has been getting all the attention, but Braddon will be a truly interesting race to watch.

Tip: Don't rule out an upset win, but Labor should hold

Mayo, South Australia

The government airdropped star candidate Georgina Downer into the SA seat of Mayo, hoping to unseat Rebekha Sharkie of the Centre Alliance (formerly Nick Xenophon Team). But the move to install Downer -- the daughter of former foreign minister Alexander -- seems to have backfired spectacularly, with the Liberal trailing badly in polls.

The latest numbers show Sharkie is ahead 62-38, and while the actual election figure will likely be a bit tighter than that, it seems South Australians have not taken to Downer.

Howard and Downer visit a Mayo shopping centre (AAP Image/Kelly Barnes)

She doesn't live in the state, and was parachuted into the Mayo race hoping family connections would win over voters. But it seems that very connection is among the reasons for her unpopularity, with talk that locals don't appreciate being taken for granted.

Sharkie is a popular local member and her connection to Xenophon does her no harm. The government has been pouring support into the Mayo race in recent days, even deploying former Prime Minister John Howard to campaign with her, but it might be too little too late.

Tip: Sharkie to hold the seat comfortably

Perth and Fremantle, Western Australia

The two WA seats should be the most straightforward. Both are held by Labor, and the government has not even bothered to field a candidate in either seat.

The Greens are likely to record a strong result in both, but these seats won't be changing hands.

Dual citizen MP Josh Wilson will return to parliament as Member for Fremantle, while Patrick Gorman will almost surely come into parliament as the new MP for Perth, replacing Hammond.

Tip: Labor to hold both