This weekend political nerds are getting a very, very early Christmas present: five by-elections across the country that have the potential to shake up federal politics massively. Here’s what you need to know so that you can hold a conversation with your parents/mates/dog without breaking a sweat.

Back in May, the High Court took the scalps of four members of parliament. Centre Alliance’s Rebekha Sharkie, and Labor’s Susan Lamb, Justine Keay, and Josh Wilson, were all told they couldn’t sit in parliament because they had foreign citizenships when they nominated to enter federal politics.

But these by-elections are shaping up to be a tough test for both sides of politics. Campaigning has been heated. As opposition leader Bill Shorten and PM Malcolm Turnbull have travelled the country electioneering, their candidates have endured a wild campaign that’s had everything from controversy over military medals to one of the weirdest robocalls in Australian political history.

Here Are The Details

There are five by-elections on Saturday — four because of the dual citizenship crisis, and one in Perth that came about after Labor MP Tim Hammond resigned for family reasons. Labor will win the by-elections in Perth and Fremantle — the Liberal Party didn’t even bother putting up candidates to compete against them. But it’s worth knowing what’s happening in the other three by-elections.

Longman

WHO: Labor’s Susan Lamb is fighting to reclaim her highly contested seat against the LNP’s Trevor Ruthenberg.
WHERE: Longman is in Queensland, squeezed between Brisbane and the Sunshine Coast.
PREDICTION: Too close to call. Recent polls have Rutherberg at 51 percent and Lamb at 49 percent.

"It's weird, it is grubby, it's small scale. But it just makes you think what kind of guy is it that would do this little pointless tweaking on his CV?" David Marr says of LNP candidate for #Longman Trevor Ruthenberg #Insiders #auspol pic.twitter.com/guY7SYAPON

— Insiders ABC (@InsidersABC) July 21, 2018

In 2016, this seat came down to the wire: Susan Lamb was able to snag it on a 0.8 percent margin — that’s nothing.  The seat has flip-flopped between Labor and the LNP over the past decade — Australia’s youngest ever MP Wyatt Roy held it before Lamb.

Recent coverage on the Longman by-election has been dominated by reports that the Liberal Party’s Trevor Ruthenberg had lied about what military service medals he had been awarded. “Big Trev”, as the prime minister calls him, claimed to have received a medal of distinguished service while on peacekeeping and non-war operations. He had actually been awarded a less prestigious medal.

Despite their poor showing at the most recent Queensland state election, One Nation is still a party to keep your eye on in Longman. Because the margin will likely be tight, and because One Nation is polling at a solid 13 percent, the way their preferences flow may decide who wins.

And in one for the history books, ex-Labor leader Mark Latham recorded a robocall attacking the ALP — the party he once led — and threw his support behind Pauline Hanson’s One Nation. Meanwhile, Hanson has gone on holiday and One Nation’s candidate might owe some people quite a bit of money.

Braddon

WHO: Labor’s Justine Keay will fight for her political life against the Liberals’ Brett Whiteley.
WHERE: Braddon covers much of the western half of Tasmania.
PREDICTION: Labor, but it’s close. Recent polls have Keay on 52 percent and Whiteley on 48 percent.

Keay and Whiteley have both won elections in Braddon before: in 2013 Whiteley entered parliament before getting ousted in a close election by Keay. Keay held Whiteley by a 2.2 percent margin back in 2016, and polls suggest that this by-election will be a close one.

Both Shorten and Turnbull have tried their hardest to appeal to the Tassie voters ahead of Saturday: earlier in the month, Shorten promised to set aside $25 million for the creation of a Tasmanian AFL team.

As with Longman, if the election ends up being close the result could come down to minor party preferences.

Mayo

WHO: Centre Alliance’s Rebekah Sharkie (formerly part of the Nick Xenophon Team) is facing off against the Liberal Party’s Georgina Downer.
WHERE: Mayo covers the south of Adelaide and Kangaroo Island.
PREDICTION: Polls have Sharkie leading Downer 62 percent to 30 percent.

The Liberal Party won every single election in Mayo’s history — until 2016. As part of Nick Xenophon’s extraordinary, short-lived surge, Sharkie won against the LNP’s Jamie Briggs with a respectable margin of five percent.

This is how the LNP is responding to Labor attack ads in Longman @SkyNewsAust pic.twitter.com/GwqItdlwxH

— Jackson Williams (@jacksonw____) July 24, 2018

Downer, who is the daughter of former foreign minister Alexander Downer, has a tough road ahead of her. She’s struggling to shrug off the perception that she’s too privileged to represent a blue collar district, and her opponent has set up an impressive ground game: the ABC reports that Sharkie has raised $65,000 in grassroots donations and has an army of 800 volunteers on the ground for her.

In recent days attention has focussed on Sharkie’s proposal to build a bridge between Kanagaroo Island and mainland Australia: something that critics fear would cost billions and wouldn’t be that useful.

The Liberals would have hoped to win the seat back, but it doesn’t look like that will happen.

Why Do These By-Elections Matter?

Whatever happens on the weekend, the Liberal Party will still be in government and Labor will still be in opposition — but there’s a lot more at stake.

Because all of Australian politics focuses on these mini-elections so intensely, the results of by-elections have outsized influence. Losses in by-elections the year before a national election are often viewed as a signal of things to come and can have dire consequences for leaders on the losing end.

The good news for Malcolm Turnbull is he can’t possibly lose — none of his party’s seats are up for grabs — while Bill Shorten has a lot on the line.

Jobs, education, health – that’s what’s important to the people we're fighting for, and that’s what’s important to Labor. pic.twitter.com/mATQFP3OYP

— Bill Shorten (@billshortenmp) July 22, 2018

Expert political commentator Michelle Grattan summed it up like this in The Conversation:

“We know from history that key by-elections can have big political impacts,” she wrote. “And that’s been when there was only one on the day.”

And here’s an extraordinary statistic: a government hasn’t successfully taken a seat from the opposition party at a by-election for almost 100 years.

All this spells trouble for  Shorten. If he loses one or both of the close by-elections this Saturday, that could kick off speculation about whether he’s right to lead the Labor party.

One Galaxy poll suggested that if Anthony Albanese — Shorten’s main leadership rival — were in charge, the party would comfortably get over the line in both Longman and Braddon.

That’s a trend repeated nationally. Labor remains ahead of the government in the polls, but Shorten is personally unpopular. The thinking goes that Labor would be miles ahead if someone else was in charge. The rumblings will only intensify if Labor loses a few seats this weekend.

Last month in a speech to the Labor faithful, Albanese set out his vision for the party — a ploy which many pundits saw as a move towards a leadership challenge.

Keep an eye on all five by-elections this Saturday — but in particular the ones in Longman and Braddon. If preferences flow the wrong way and voters aren’t in the mood, it’ll be far from a “Super Saturday” for Shorten.