Stakes are high for both parties in upcoming Dunstan by-election | Kathryn Bermingham

The by-election caused by the resignation of Steven Marshall will be a litmus test for both the government and the opposition, writes Kathryn Bermingham

Steven Marshall’s decision to resign from parliament will set up a by-election showdown with wider implications for both parties.

Held by the Liberals in 2022 with a margin of just 0.5 per cent, the seat is wide open and Labor will be looking to strike.

Since the election, there has been consistent speculation that Mr Marshall would resign midterm.

But his slender lead meant the Liberals needed to be strategic with their timing and carefully predict when they would have the best chance of winning.

Clearly, they believe that time is near – however the Liberals have left themselves some wriggle room, with Mr Marshall yet to set a date for his resignation.

His statement on Wednesday only went as far as saying he was currently “signalling his intent to retire” and would formally resign “over the coming months”, meaning voters could be in for a lengthy campaign.

“I think that the by-election will be around the halfway point of the cycle,” he said when pressed on the date.

“I don’t want to put an exact date on it.

Steven Marshall on the backbench in parliament. Picture: NCA NewsWire/Kelly Barnes

“By announcing it today that I will be resigning in the coming months, it gives the party the chance to preselect the very best candidates, get out there and give ourselves the best shot for the by-election.”

By making the decision near the mid-way point of the electoral cycle, the Liberals will be hoping that Dunstan voters are frustrated and ready to punish the government.

Mr Marshall called the by-election a “referendum” on the Labor government, which he said was “elected on a single promise to fix ramping by any measure”.

“They haven’t done that, in fact, I think it’s the worst in the history of South Australia,” he said.

Opposition Leader David Speirs indicated the Liberals will look to make health and the cost of living their key by-election issues.

But a win is by no means a given, and the loss of another seat would be a crushing blow to the opposition’s efforts to rebuild.

As its name suggests, the seat has traditionally been a Labor stronghold and, given Mr Marshall has held it since 2010, it is reasonable to suppose he has an incumbency benefit.

The Liberals will look to use the long lead-up to replicate some of that recognition for their preselected candidate.

The widely touted frontrunner, lawyer and former staffer Dr Anna Finizio, is already active in the electorate – as is Ms O’Hanlon, who is expected to run again for Labor.

The task ahead will be difficult for her too, with history proving it near-impossible for governments to win opposition seats at by-elections.

At the halfway point of the election cycle, the looming poll will be a temperature check in the lead-up to 2026.

The stakes are high for both parties – and it is an opportunity that neither can afford to squander.

Originally published as Stakes are high for both parties in upcoming Dunstan by-election | Kathryn Bermingham