The battle for Longman left Susan Lamb "exhausted" but the result left her beaming as Labor swept the battleground seat as part of the Super Saturday by-elections.
A beaming Ms Lamb was joined by Labor Leader Bill shorten at the party function north of Brisbane on Saturday night.
"What a great night for Labor women! What a super Saturday it is!" he told the cheering crowd of supporters.
Ms Lamb said voters had sent a message to the Turnbull government.
"They have sent a message loud, they have sent it clearly. Stop giving big banks a tax cut and start funding our schools and hospitals," she said.
The campaign had clearly taken its toll, with Ms Lamb briefly forgetting she had four children, not two, in her victory speech, before regathering.
"It's been a long campaign, all right?" she said to laughs.
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She thanked her LNP counterpart Trevor Ruthenberg, who earlier conceded defeat and took responsibility for the result.
He praised Prime Minister Malcolm Turnbull for his support, especially during the furore over the mistake he made in describing his defence service medal.
"I have witnessed and been the beneficiary of all the character traits you would hope for in a prime minister," Mr Ruthenberg said in his concession speech.
The mood of the official Labor function at the Caboolture RSL was jubilant even early in the night with only a small fraction of votes counted.
Red-shirted volunteers hugged each other, laughed, drank and cheered as the vote count mounted in Ms Lamb's favour.
The result in Longman is a disaster for the LNP, which had seen the seat as within their grasp, with Ms Lamb holding it with a narrow margin of 0.8 per cent before her resignation after being caught up in the dual citizenship scandal which swept federal parliament.
The polls had given a slight edge to Mr Ruthenberg up until polling day itself, when they flipped and gave Ms Lamb a small lead.
That final flip in polling translated into big support for Labor on polling day itself, however the result is expected to tighten up once pre-polls are counted, which traditionally skew conservative.
LNP state president Garry Spence said Labor had spent up big to ensure it retained Longman and kept Bill Shorten's leadership safe.
"The Labor Party had to do what they could to shore up the leadership. They have spent money, bet the farm to do so," Mr Spence said.
Mr Ruthenberg's primary vote was a low 26 per cent, after he suffered a swing against him of 10 per cent.
One Nation's Matthew Stephen has eaten into the Liberal National vote, but up to 40 per cent of One Nation preferences went to Labor.
Australian Associated Press