Labor has narrowly escaped an embarrassing state by-election loss as a long-time state government concedes it must win back voters' trust.
The Victorian Labor Party claimed victory in the Werribee by-election on Friday after candidate John Lister extended his margin when more returned postal votes were counted.
The Liberals subsequently conceded defeat.
At last count, Mr Lister had received 50.71 per cent of the vote on a two-candidate-preferred basis compared to Liberal pick Steve Murphy with 49.29 per cent.
Despite the win, Labor's primary vote in Werribee, in Melbourne's outer west, has slumped 16.5 per cent.
The party has held the seat since 1979, most recently through former treasurer Tim Pallas whose resignation forced the vote.
Mr Lister, a local teacher and Country Fire Authority volunteer, was unsure whether the revolt from Labor's support base was a by-election aberration or if the seat would remain marginal in the future.
"I don't have a crystal ball," he said.
Transport Infrastructure Minister Gabrielle Williams said by-elections were tough on incumbents, suggesting the average swing was about 13 per cent.
"Our focus now has to be on demonstrating that we've heard the message, on being out there and delivering and winning back that trust," she said.
Labor knocked on about 20,000 doors during its campaign to save the seat.
"We've heard the message from voters loud and clear," Mr Lister said.
The state Labor government is on the nose after more than a decade in power, recent polls show.
A Resolve poll from early-December and mid-January showed Labor's primary vote had plummeted to a record low of 22 per cent - enough to end its reign if replicated at the next state election in November 2026.
The by-election was the first electoral test for Premier Jacinta Allan and Liberal leader Brad Battin since each respectively took over from Daniel Andrews and John Pesutto.
Ms Allan did not turn up to Werribee to congratulate Mr Lister in person on Friday but he said they had been in touch by phone.
The Victorian Liberal leader took aim at the premier's no-show, claiming she was a "problem" for the Labor brand.
Mr Battin maintained the by-election result sent a strong message to Labor that it could not keep neglecting Melbourne's west.
"I'll assure all those out in Werribee, all those out in the west, that we will continue to fight and work with them," he said.
An official result is expected to be announced by the state electoral commission after preference distributions are finalised.
Election analysts have cautioned against people reading too much into the implications of the swing away from Labor ahead of the federal election, which must be held by May 17.
The vote in Werribee was held on the same day as another state by-election in the inner eastern electorate of Prahran.
Liberal candidate Rachel Westaway came out on top of Greens hopeful Angelica Di Camillo.
The seat had been held by the Greens since 2014, with the vote prompted by the resignation of Sam Hibbins after he revealed an affair with a staffer.
The Greens blamed the loss on absentee votes not being allowed and lost preferences after Labor chose not to run a candidate.
