It might be the last by-election of the year, but the NSW seat of Bennelong could be the one that brings the Turnbull government down with an Australian political academic saying it's no longer a safe Liberal seat.
Bennelong voters will head to polling booths on December 16 after the dual citizenship crisis claimed Liberal MP and member for Bennelong John Alexander at the weekend.
Mr Alexander, who is part of Malcolm Turnbull's one-seat majority government, said he will contest the seat, which the Liberals hold by more than nine per cent.
But, it's no longer a safe Liberal seat, University of Sydney Government and International Relations Honorary Associate Professor Michael Hogan says.
"It's not something the Liberals can be confident about," he told AAP on Monday.
"It's normally regarded as a safe Liberal seat but it's not."
Labor has only claimed the seat once before when the then-Prime Minister John Howard lost to Maxine McKew.
Prof Hogan says it can be done again and will depend on Prime Minister Malcolm Turnbull's ratings during the campaign.
"The normal expectation is that people tend to vote against the government because there's nothing weighing on it usually but this time there is, if they lose, they will be challenged to hang onto the government," he said.
Federal Opposition Leader Bill Shorten conceded his party will have a tough fight.
"Labor is behind the eight ball ... it is a 10 per cent margin for the Liberals, but we are going to give it every effort because the nation deserves to have a choice about the direction in which the nation is headed," Mr Shorten told reporters in Canberra on Monday.
It's a different story in the state's New England region where Barnaby Joyce is the only serious candidate, Prof Hogan says.
Mr Joyce decided to recontest the seat after he was forced to step down over his New Zealand citizenship.
"No one is standing against him that can win," Prof Hogan said.
Bill Cahill, who has lived in the Bennelong suburb of Epping for most of his life hopes Labor takes the seat.
"I would much prefer a Labor MP," Mr Cahill told AAP on Monday.
"It's bad that this has eventuated ... it's a waste of money and a waste of time, particularly at this time of the year when politics should be right out of the forefront."
