Labor’s Susan Lamb won Longman with 0.8% margin, but polling says Coalition will win it back in byelection.
Photograph: Mick Tsikas/EPA

New polling shows the Turnbull government could take the marginal Queensland seat of Longman from Labor at the looming byelection triggered by the dual citizenship fiasco, with the One Nation vote sitting on 15%.

A new ReachTel survey of 1,277 residents across the federal electorate of Longman taken on Thursday night has the LNP polling ahead of Labor on two party preferred terms 53% to 47%.

But the research, funded by The Australia Institute, also suggests the Turnbull government’s proposal to cut tax for Australia’s biggest businesses is unpopular, with only 17% endorsement.

Voters were asked whether they supported or opposed tax cuts delivering an average of $530 a year extra for low and middle income earners in the first four years, and tax cuts for high income earners in seven years time.

More Longman voters opposed the measure (47.3%) than supported it (38.3%).

If Labor lose any of the byelections in seats it holds it will be too embarrassing for words.

Consistent with a Guardian Essential poll published the day before the budget, more people supported funding for service delivery (43.5%) than tax cuts (19.2%), with 28.8% saying revenue should be used to decrease debt and pay back the deficit. Only 1.9% of the sample nominate tax cuts for corporations as a priority.

The Labor incumbent in Longman Susan Lamb resigned on Wednesday following the high court’s ruling in the Katy Gallagher case.

The resignations this week have triggered contests in Longman, the Tasmanian seat of Braddon, the South Australian seat of Mayo and the Western Australian seat of Fremantle. There will also be a byelection in the seat of Perth, because of the resignation of the Labor MP Tim Hammond for family reasons.

Given the contests will stretch party resources in the run up to a federal election, the Liberals are highly unlikely to run in Fremantle, which will be a Labor/Green contest, and may not run in the seat of Perth either. The Liberals are in the process of preselecting candidates for Longman, Braddon and Mayo.

The Labor incumbents will defend their seats, as will the Centre Alliance MP Rebekha Sharkie, who resigned on Friday.

Sharkie is the most likely casualty from the upcoming super Saturday of byelections triggered by the latest wave of dual citizenship resignations, analysts have said.

Sharkie won the formerly safe Liberal seat in the Adelaide Hills on preferences in 2016, with the help of an unpopular opponent in former MP Jamie Briggs and the once-powerful campaign clout of then senator Nick Xenophon.

Sharkie’s party has been rebadged from the Nick Xenophon Team to the Centre Alliance, but Flinders University associate professor of politics, Haydon Manning, whose wife ran for SA Best in the state election, said volunteers and donors felt burnt by the recent loss.

“[Sharkie] doesn’t have the money, she doesn’t have the database,” Manning said. “But she has been the incumbent for two odd years, she has worked tirelessly, she has got good demeanor, and she is a person that this seat has not had, in that she is focused on the community.”

Internal Liberal party polling in Tasmania suggested the Coalition was in front in Braddon 53-47, but Tasmanian election analyst Kevin Bonham said it was based on an “utterly woeful” sample size and should be dismissed.

Braddon has a history of swapping sides and has not been held for more than two consecutive terms since 1998. Labor’s Justine Keay won it in 2016 and has a 2.2% margin.

Bonham said he expected Labor would retain all four of its seats, failing a catastrophic campaign mistake on behalf of one of its candidates, or a superstar candidate from the Liberal Party.

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“If they lose any of them it will be too embarrassing for words,” he said.

He said Longman, which Lamb won from the LNP’s Wyatt Roy in 2016 on an 0.8% margin, was the most at-risk Labor seat.