Vote counting is underway in the Black electorate of Adelaide’s south, with early results showing a “big swing” to Labor, according to the ABC’s chief election analyst, in what could be a hammer blow for the SA Liberals.

The by-election was called last month after the seat was vacated by former Liberal leader David Speirs, who quit parliament after being charged by police with supplying a controlled substance.

Almost a third of the electorate had their say before polling day, with around 8,500 of the more than 26,000 eligible voters voting early.

Counting of those votes will not begin until Monday, meaning the outcome of the by-election may not be known tonight.

But the ABC’s chief election analyst Antony Green said early results suggested a “huge swing” to Labour.

“Second polling place and a big swing is on,” Green tweeted.

“Unless Labor voters didn’t turn up today and the Liberals didn’t all go to pre-voting, Labor will win the Black by-election.

“A government hasn’t taken a seat from the opposition in a by-election in a century and now we have two in one term.”

The Black electorate was created during a 2016 boundary redistribution and was easily won by Mr Speirs in the 2018 state election, but became marginal four years later.

While Mr Speirs retained his seat in 2022 with 2.7% on a two-party preference basis, there was a 6.5% swing to Labor candidate Alex Dighton.

Mr Dighton is again contesting the seat for Labor, with Holdfast Bay Mayor Amanda Wilson running for the Liberals.

The Liberals have more at stake politically in the vote.

While a Liberal victory would not change the numbers in state parliament, a Labor victory would further erode the state opposition’s parliamentary presence and compound the damage caused by the Liberals’ defeat in March’s Dunstan by-election.

Regarding the polls earlier today, Mr Tarzia acknowledged the importance of by-elections.

“We’re working very hard to make sure we get back in the black – we get back in the black and get South Australia back on track,” he said.

“This is the battle for Black today. Whatever happens, we’re focused on winning the war and making sure we hold the government to account, that we put forward an alternative set of policies.”

Asked about the political significance of a potential Labor victory, the Prime Minister said he would “leave that to the commentators”.

“My responsibility is to keep delivering for the state, we just have to keep doing things,” Mr Malinauskas said.

“There are difficult economic circumstances, but South Australia is outperforming the rest of the country.

“That approach will not change regardless of today’s result.”

“Million Dollar Question”

Both major party candidates today spoke about the cost of living as a hot-button issue for voters.

Ms Wilson said it was evident from her campaign that there was a “sympathy” for David Speirs that “resonated deeply in the community”.

The Liberal candidate was asked how much Mr Speirs’ personal popularity in the seat would influence the outcome.

“David was a very popular local member and of course it was a very close race.”

Mr Dighton said he was “very proud” of Labor’s campaign in the seat.

“We’ve knocked on 7,500 doors in the last few weeks,” he said.

“I am very confident in what we have proposed.”