The South Australian Liberals have clung onto official opposition status, but they are still feeling the pain of One Nation’s breakthrough.

There were scenes of Liberal jubilation in Stirling last Saturday when deputy leader Josh Teague held onto his Adelaide Hills seat of Heysen, the result ensuring the Liberals would remain the largest non-government party in the lower house.

“I couldn’t be prouder Josh to be with you – I can’t wipe the smile off my face,” Liberal leader Ashton Hurn said, before being embraced by her deputy in an impromptu on-camera hug. 

But there’s been plenty to bring down the mood since. 

Josh Teague is smiling next to Liberal leader Ashton Hurn as she stands behind a group of media microphones

Josh Teague and Ashton Hurn in Stirling on Saturday March 28, after Mr Teague held onto his seat of Heysen. (ABC News: Daniel Taylor)

On Sunday, Liberal frontbencher Stephen Patterson lost his coastal seat of Morphett to Labor – the fifth seat the government has taken from the Liberals this election.

A hit from the left in Adelaide was followed by a blow from the right in the regions: One Nation on Monday were deemed winners in the South East seat of MacKillop. 

The electorate, formerly held by ex-Liberal turned independent Nick McBride, was a rare opportunity for Ms Hurn’s party to pick up a seat, but it fell short by about 400 votes. 

Then on Thursday, One Nation secured its fourth seat with a narrow victory over the Liberals in the Yorke Peninsula seat of Narungga. 

When Ms Hurn and Mr Teague were celebrating in Stirling, the Liberals had an outside chance of holding eight seats; they will now go into the next parliament with just five, and an emboldened One Nation breathing down their necks.

Ciry Bernardi speaks behind a group of media microphones and flanked by a group of elected One Nation members

SA One Nation leader Cory Bernardi addresses the media in Adelaide with his newly elected team. (Supplied)

“I want to be the official opposition,” One Nation SA leader Cory Bernardi said on Wednesday, flanked by his new parliamentary colleagues.

“I think there’s even a moral case that you could say we should be the official opposition in this state.”

Ms Hurn hit back on Thursday, replying: “The English cricket side said that they had the moral victory over Australia in the Ashes – it didn’t mean that they won the Ashes.”

“The rules are the rules, and we are the formal opposition.”

Everyone stay on the ship

The upshot of all this is Ashton Hurn now has very little margin for error.

Her party’s performance over the next four years can be nothing like the last four, which saw three Liberal MPs resign and two defect to the crossbench.

One Nation’s moment arrives in SA. It might only be the beginning

If it can happen in South Australia, it can happen anywhere.That’s the takeaway from One Nation’s performance at this state election.

That shrunk the party’s lower house numbers from 16 to 13. With it now down to five, there is simply no longer any fat in the caucus for resignations or defections. 

If that does happen, the party’s status as the official opposition gets dicey. 

Constitutional law expert Anne Twomey said if One Nation ended up with equal or more MPs than the Liberals during this term of parliament, it would be up to the speaker of the house to decide the official opposition.

“One Nation would no doubt say that they wanted a change made and to become the opposition and the opposition leader, and it would be up to the speaker to make a decision,” she said.

A woman wearing a green jacket smiling

Professor Anne Twomey says the speaker of the house will decide the official opposition if One Nation ends up with equal or more MPs than the Liberals. (ABC News: Liam Patrick)

Professor Twomey added that there were “no real conventions or rules” about how the speaker would act, particularly if the Liberal Party and One Nation had equal numbers.

“They might take things into account like proportion of first preference votes, they might take into account history in terms of the stability of the party, defections et cetera [or] are they actually able to form an alternative government that could end up being elected the next time around?” she said. 

“But the reality is there’s been so few precedents about this in Australia or indeed in other comparable countries that we don’t really have any proper rules or conventions. 

Liberals to retain SA opposition status, ABC projects

The ABC is projecting that the Liberals have retained the Adelaide Hills seat of Heysen, meaning the party will be the second largest in the House of Assembly and retain opposition status.

“It’s really just a matter of what the relevant speaker, or indeed the house, thinks is appropriate in the circumstances.”

With the speaker of the lower house likely to be a Labor MP, it is hard to imagine them favouring a One Nation opposition over the Liberal Party. 

Labor preferenced the Liberals over One Nation at the election. Premier Peter Malinauskas also declared he would rather see the Liberals form government than One Nation.

If the speaker did not act and kept the status quo, Professor Twomey said MPs could table a motion of dissent to decide the opposition.

“If there’s a vote in the house about it, it’s possible the government could abstain,” she said. 

In that unlikely scenario, the Liberal Party, One Nation and the four independents in parliament would be left to thrash out the opposition.

Pressure on One Nation too

All the above will almost certainly be avoided if Ms Hurn keeps her team together for four years, and there is evidence to suggest the Liberal Party is more united under her leadership than her predecessors.

One Nation beset by defection

One Nation is no stranger to internal rumblings, and its latest imbroglio has occurred in South Australia, where state upper house MP Sarah Game recently announced her decision to quit the party and become an independent.

Ms Hurn brushed off a question on Thursday as to whether she was worried MPs would leave the party and jeopardise its opposition status.

“You can hear some of the laughs behind me, I think that tells you the answer,” she said, referring to her new shadow cabinet standing in the background.

There is also plenty of pressure on One Nation to stick together given its history of disunity.

The party’s breakthrough at the 1998 Queensland state election – where it garnered an almost identical share of the primary vote (22.6 per cent) as it did at the South Australian election just gone – was followed by the almost complete disintegration of the 11 MPs it elected to parliament. 

A group of four men and a woman sit around a table in an outside area near a city street

Newly elected SA One Nation members Robert Roylance, Carlos Quaremba, David Paton, Chantelle Thomas and Jason Virgo. (ABC News)

The party is yet to prove its stability in SA either. Its first MP elected to state parliament, Sarah Game, defected last year, prompting a wave of party recriminations. 

Pauline Hanson has described One Nation’s new MPs in South Australia as “landmines”. 

The next four years will reveal which party is collateral damage.