Bennelong voters head to the polls on Saturday as the Coalition government's grip on Parliament hangs in the balance, in what is shaping as an acid test of Prime Minister Malcolm Turnbull's leadership.
Labor candidate Kristina Keneally hit the hustings with zeal but remains an outside chance of defeating former tennis champion and Liberal incumbent John Alexander, who was last returned to the lower north shore seat in 2016 with a margin of almost 10 per cent.
Both parties have poured resources into the heated byelection campaign, which was triggered when Mr Alexander resigned from Parliament after Fairfax Media revealed he was likely a dual British citizen by descent.
While Mr Alexander is expected to narrowly retain the seat, a swing towards Labor would portend trouble at the next federal election for the government, which clings to power with a one-seat majority in the lower house.
Mr Turnbull underlined the high stakes on Friday, warning that a vote for Ms Kenneally was a "huge risk".
"Thousands of jobs and the future of millions of Australians depend on John Alexander being returned once again," he said.
"There's no doubt that if Kristina Keneally is elected, we will be down to just 75 votes in the House of Representatives. This will bring [Labor leader] Bill Shorten closer to being prime minister."
Should the government lose Bennelong, it could still govern as a minority government but it would be forced into unpredictable negotiations with the crossbench to pass legislation in the lower house.
A Newspoll published on Tuesday put the rivals at 50-50 on the two-party preferred vote.
A Fairfax Media-ReachTEL published two days later had Mr Alexander leading Ms Keneally 53-47 on a two-party preferred basis.
Throughout the campaign the government attacked Ms Keneally over her record as NSW premier and links to disgraced former Labor MPs Eddie Obeid and Ian Macdonald.
Ms Keneally has campaigned on bread-and-butter issues such as health, hospital and education funding, and says the government has failed on the NBN rollout and electricity prices.
"This Saturday ... is an important election. It is an opportunity for the people of Bennelong to stand up and have their choice heard," she said on Friday.
Around half of respondents to the ReachTEL poll said revelations about Labor senator Sam Dastyari's connections to China will affect their vote.
However Labor claims the government's China-phobic rhetoric has eroded its support in Bennelong, which has a large Chinese-Australian population.
A Labor breakdown of the margins in every federal seat shows that a swing against the government in Bennelong of up to 2 per cent, if repeated uniformly across the nation at the next federal election, would see it lose 12 seats.
It means Mr Turnbull's leadership could remain under a cloud even if the Coalition retains Bennelong on Saturday.
In an interview with 3AW's Neil Mitchell on Friday, Mr Turnbull appeared to reject suggestions the byelection was a direct test of his leadership.
"People will be casting a judgment on the government, which I lead, of course," he said, adding his leadership was a "matter for the Liberal party room".
