Coalition expected to hold Fadden in key by-election

Senior federal Liberal MP Karen Andrews called the result for the coalition within the hours of the polls closing at 6pm.

"It's clearly not a good night for Labor based on these figures," she told Sky News on Saturday.

"I know they would say that they expected that they would lose some margin in this election but ...they were putting their heart and soul into trying to do damage to the LNP.

"For Labor, this is a very disappointing outcome and maybe they need to rethink some of their strategy."

Cost of living was the main issue for voters in the northern Gold Coast seat, according to Mr Caldwell who will replace former coalition minister Stuart Robert.

Asked earlier on Saturday if Mr Robert's involvement in the robodebt scandal that engulfed the previous Liberal-Nationals federal government would impact voters Mr Caldwell said they had other things on their minds.

"Those are issues that are really starting to bite in their households and it's whether people can put food on the table and keep the lights switched on," he told Sky News.

"That's really what's on their mind as they walk into the polling booth today."

Under Mr Robert, whose resignation from parliament in May triggered the by-election, the LNP held the seat with a margin of 10.6 per cent after the 2022 national poll. 

Robodebt is the name given to an unlawful debt recovery program that saddled almost half a million welfare recipients with hundreds of millions of dollars in false Centrelink debts between 2015 and 2019.    

A royal commission investigation into the scheme released earlier this month laid the blame at the feet of senior public servants and coalition ministers including Mr Robert, Scott Morrison, Alan Tudge and Christian Porter.

Labor had tried to use this to bolster its candidate for Fadden, Ms Del Fabbro, who said earlier on Saturday any swing to Labor would be a blow to the coalition in one of their safest seats.

Ms Del Fabbro, who is contesting the seat for the second time, was credited with whittling down Mr Robert's margin from 11.2 per cent at the 2019 federal election to 10.6 per cent.

"Any swing against the LNP would be a loss to them," the nurse educator said as she cast her vote.

But she agreed cost of living issues had dominated the campaign, although there was also interest in the robodebt scandal and the Indigenous voice to parliament.

Treasurer Jim Chalmers said the average swing against a government in a by-election was about four per cent so anything less would be embarrassing for Opposition Leader Peter Dutton.

Labor has won Fadden only once - in 1983 under the election of the Hawke government.

A total of 13 candidates are running in Fadden including from the Greens, Pauline Hanson's One Nation and the Australian Democrats.