The Liberal party is staring at a historic loss in the Wentworth by-election and a tenuous hung parliament as the race tightens.
Held by the Liberals since the party's inception, voters have signalled they will shake things up in the once safe blue-ribbon seat at Saturday's poll.
Even Prime Minister Scott Morrison was pessimistic when asked on Friday whether he expected Liberal candidate Dave Sharma to lose.
"I think the expectations are clearly set in this direction," Mr Morrison said.
Nationals MP Darren Chester was also blunt.
"I don't think the Wentworth by-election will be good for the government," he told ABC radio.
"I think we're about to get a real-life opinion poll on what Australians think of political parties that undermine their leaders and change leaders mid-stream."
The government's one-seat majority hangs in the balance and a hung parliament looms as Mr Sharma faces fierce competition from independent Kerryn Phelps.
The bookies have installed Dr Phelps as firm favourite at $1.33 with Mr Sharma out to $3 to claim the seat vacated by former prime minister Malcolm Turnbull when he was knifed in August.
Mr Morrison says there's much at stake with internal Liberal polling suggesting Dr Phelps could defeat Mr Sharma as party faithful vent their anger about Mr Turnbull's axing.
Mr Turnbull won the Sydney seat at the last election with a 17.7 per cent margin.
"I accept and understand that anger and outrage," Mr Morrison said at Bronte Beach on Friday.
"We have heard that the leading independent candidate has said she could not guarantee not bringing down the government on a vote of confidence in the government. Now, that is serious stuff."
A non-Liberal victory would create "unnecessary uncertainty," he said.
Dr Phelps pointed the finger back at the government, saying she was keeping her options open but didn't have any agenda to oust them via a no-confidence motion.
"I think we've seen enough recklessness and chaos," she told AAP.
"In terms of a no confidence motion, I think it would be reckless to make any kind of prediction about that without knowing what the circumstances might be."
The independent confirmed seeking legal advice over her eligibility to run, making sure she won't breach the constitution by working as a GP and councillor if she wins.
While Dr Phelps said she sensed a "momentum for change" among voters, she cautioned against being overly confident.
Mr Sharma, a former Australian ambassador to Israel, is running on 45 per cent of the two-party preferred vote compared to 55 per cent for Dr Phelps, internal polling suggests.
The Liberal candidate said it was always going to be a difficult campaign because of "unique circumstances" sparking the vote.
"There's no doubt this is going to be a close by-election," he told AAP.
"This is a choice for voters: Do they want to keep a one-seat majority government in Canberra with strong economic credentials and a reform agenda?"
Mr Sharma has had a difficult final campaign week as the government lurched from one gaffe to the next.
Mr Sharma also had to condemn a "despicable" anonymous email circulating falsely claiming Dr Phelps was pulling out of the race because of a HIV diagnosis.
