Voter unhappiness in the formerly safe NSW Liberal seat of Willoughby goes back at least three years, and the swing in last Saturday's by-election should be "no surprise", the independent challenger says.
Larissa Penn said when she ran against former premier Gladys Berejiklian in 2019 there was already "growing discontent across a range of issues" in the northern Sydney electorate.
"I was getting contacted every day by the community (urging me) to run," she told AAP.
"I'm involved in lots of different community groups, environment groups, P&Cs, advisory groups to council," she said, adding her backers were also heavily involved in the community.
The most recent count puts Liberal candidate Tim James ahead at 51.8 per cent, with Ms Penn at 48.2 per cent in two candidate preferred terms, with a swing against the Liberals of 19 per cent.
Ms Penn said Willoughby voters have a range of concerns, and want politicians to make "evidence-based decisions" that put public interest first.
She said locals had "great difficulty" accessing information like contamination reports and businesses cases, which informed how projects like the second Harbour tunnel and Beaches Link would impact their community.
"We've had to lobby very hard just to get the basic information released to the community and we're still having that issue," she said.
Respect for nurses and teachers had also become a key issue as the electorate was a large catchment for schools and hospitals, including Royal North Shore.
The final results in Willoughby may not be known until later in February due to a surge in postal votes.
The NSW Electoral Commission will count a large amount of those votes on Saturday.
The swing was an "extinction level event" for the Liberals, federal Labor frontbencher Bill Shorten said.
"There's state issues at play, and state and federal are not identical," he told Australia Today radio.
"But events like that in Willoughby are extinction level events for parties counting on safe seats."
He acknowledged while the Liberals were clearly "on the nose", Labor could not afford to be complacent while "people are looking at third parties".
"You wouldn't want to be a Liberal with that result, but I don't think Labor should be complacent at all.
"We need to go out and make the case every day."
NSW Premier Dominic Perrottet said he felt comfortable his party would retain the seat, despite it sitting on a knife's edge.
"I'm still confident Tim James will be elected, as I've always said," Mr Perrottet said on Thursday.
"The people of Willoughby will choose well.
"The counting will take place over the next couple of weeks and we'll wait and see."
Opposition Leader Chris Minns said the community has "clearly sent a message" to the government.
"We've been very open and honest that we regard this as a message to the NSW premier in terms of good governance and decision making," he said on Friday.
"I think it's a wake up call for Dominic Perrottet. Listen to the experts. Listen to the community.
"Make decisions based on common sense, best available data. Not your own instincts."
Mr Minns expects the Liberal candidate will win the seat when all postal votes are counted.
