A byelection in the Brisbane seat of Stafford is expected to swing towards the sitting LNP Queensland government in a result experts say would likely be fatal to former premier Steven Miles’ leadership of the Labor party.

Voters in the northern Brisbane electorate of Stafford have gone to the polls after the sudden death of former independent MP Jimmy Sullivan in April.

If Queensland Labor loses the seat, it would be the first state party in 50 years to lose a byelection to the government from opposition, heaping pressure on Miles.

Sullivan – who had a 6.83% swing against him in the 2024 election – was expelled from the Labor party in May 2025 over legal and medical concerns.

He was expelled from Labor in 2025 after taking a months-long leave of absence and then coming under repeated personal attack by the government in parliament.

Stafford – a historically working class suburb in north Brisbane – has been almost continuously held by Labor since 1989. From 2001 to 2006 it was held by Sullivan’s father, Terry Sullivan.

With a margin of 5.3%, it was the 12th-closest Labor seat at the 2024 election and is considered marginal.

The Greens’ how-to-vote card did not recommend its voters preference either Labor or Liberal National parties, unlike in 2024.

One Nation did not stand a candidate.

Political experts have warned that the result would have ramifications for David Crisafulli’s ruling LNP government, the Labor opposition and federal politics.

Griffith University political scientist Paul Williams said it was increasingly likely Fiona Hammond would snatch the seat for the LNP with a predicted vote of 51-52% after preferences are allocated.

Notionally, Labor, whose candidate, Luke Richmond, cast his vote with his wife, Maddie, early on Saturday, still holds the seat with a 5.3% two-party preferred margin.

Recent polling shows the LNP on track for an unexpected and historic victory.

With byelection swings towards a sitting government rare, Williams said even a reduction in Labor’s margin would technically be a loss for Labor and Miles.

“If [the LNP] bring it from 55 to 53, that’s technically a loss for Labor,” Williams said. “They should be winning this seat with 59-60 and we know that’s not going to happen.

“If they lose the seat, it’s huge. If it was a regional seat, maybe, but to lose a seat in Brisbane for Labor is very consequential.”

He said a loss would likely be terminal to Miles’ leadership, with the shadow treasurer and shadow minister for women, Shannon Fentiman, best placed to challenge.

Williams said One Nation had erred by failing to stand a candidate in the urban seat, where the party has historically struggled to get traction.

“They wouldn’t win it, but six months ago it would have been impossible and now it’s moved from impossible to unlikely,” he said.

Where previously the party might have expected to poll between 2% and 4% of the vote, on Saturday it might have expected to hit between 12% and 20% or even more.

That sort of result, Williams said, would have almost guaranteed an LNP victory on preferences.

He said the Greens’ decision not to allocate preferences would likely only be consequential in the event of a very close result.

On Friday, Miles said the byelection was an opportunity for voters in the seat to send the Crisafulli government a message.

He said the outcome of the election would not change either the government or the leadership of the Labor party.