SA Liberal leader David Speirs under mounting pressure as his party faces losing the state’s most ­marginal seat of Dunstan

The SA Liberals look doomed to lose a seat from opposition for the first time in 116 years and recriminations are flying, with leader David Speirs in the crossfire.

The South Australian Liberals are in turmoil, and its leader under mounting pressure from within, as the party faces losing the state’s most ­marginal seat former premier Steven Marshall quit.

In what would be a historic victory more than a century in the making, Labor is poised to snare the inner-eastern suburbs seat of Dunstan after one of the most bitter by-elections in memory.

While senior Liberals believe their candidate, lawyer Dr Anna Finizio, 37, has an outside shot of victory, Labor officials predict their contender, businesswoman Cressida O’Hanlon, 51, will secure a seat she narrowly lost to Mr Marshall in 2022.

Anna Finizio and Liberal leader, David Speirs at the Dunstan by-election function. Picture: Brett Hartwig

The likely win, which Labor MPs attributed to Premier Peter Malinauskas amid a ­surging Greens vote and preferences, will mean the state government’s lower house majority will increase to 28 seats to the opposition’s 14.

Amid calls for urgent reforms, the SA Electoral Commission will on Monday count postal and early votes, which is more than a third of ballots.

Liberal recriminations flew Sunday night as internal anger erupted over a lacklustre campaign that critics said failed to counter the Greens “protest” and forensically check Dr Finizio’s background with her directorships or applying for a Labor job four years ago.

Ahead of a meeting on Monday night of the party’s state executive (or board), David Speirs’ leadership also came under increasing pressure as critics lashed his role and that of state director Alex May.

“There were multiple problems, but not being local and having more baggage than a Qantas carousel is a start,” one senior Liberal said.

Another said: “This is a loss which can be chalked up to missing the mood of the electorate with a safe and predictable campaign.”

A third said: “I am so angry, I don’t usually rant to journos, but I’m making an exception. Two-thirds of the party are furious, but don’t know what to do.”

Other Liberals said there were no other “credible” leaders and noted a swing against Labor in a seat that was “challenging” to win.

Labor candidate for Dunstan, Cressida O'Hanlon talking to the media at Flinders Medical Centre in Bedford Park on Sunday, which is outside her electorate. Picture: Matt Loxton

Mr Speirs, who is said to currently enjoy his MPs’ support, went to ground and failed to appear with Dr Finizio on Sunday, or return calls after he refused to take questions at a party event on Saturday night.

But in a statement issued through a party spokesman, he praised Dr Finizio – who currently has 46.2 per cent of the major party vote – as a “tremendous candidate who gave the campaign her all”.

“With thousands of early votes still to be counted, it’s too early to officially call it, but on the current numbers, it’s clearly a disappointing ­result for us,” he said.

“We are hopeful of a better result as early votes start to be counted, but the pathway to victory is very narrow.

“As the dust settles, we must take stock, regroup and better articulate our positive vision for South Australia.”

Ms May, whose partner is federal Liberal MP James Stevens, would not comment.

On Sunday, Liberal frontbencher Vincent Tarzia sparked leadership speculation after “making lots of phone calls”, while using phrases such as “how are you feeling” – days after hosting a major fundraiser.

Mr Tarzia, who sources said was “pondering” a challenge, did not return calls.

But in a social media post, he wrote: “We must respect the result, listen to the feedback and move forward.”

More than 9300 votes, out of 27,108 enrolled electors, are yet to be counted, which Liberals believe they have a 25 per cent chance of winning, in what may mirror a six per cent turnaround to Bragg MP Jack Batty in last year’s by-election.

If Ms O’Hanlon, a mother of four and former political staffer, wins it would be the first time a SA government has taken a seat from an opposition at a by-election in more than 116 years.

Mr Malinauskas – who appeared jubilant at Labor’s electoral success, as Ms O’Hanlon fronted a press conference at Flinders Medical Centre on Sunday which is in Adelaide’s south, outside of her electorate – has also tried to inflame Liberal leadership tensions, but would not weigh in on Sunday.

He said a swing away from the government was normal.

“We don’t let that get to our head, we just get on with the task,” he said.