Prime Minister Julia Gillard has called a ballot for the Labor leadership after supporters of Kevin Rudd took the first steps towards another spill.
Ms Gillard says the spill will be held at 7.00pm AEST, and that whoever loses should retire from Parliament immediately.
She is responding to a petition from Rudd supporters calling for a vote and has little to lose.
If she leads the party into the election, polls indicate it will be decimated and she would have to resign the leadership anyway.
The question her MPs will have to ask is whether the party will stand a better chance under Rudd.
He appears to be more popular with the public than his own caucus which is not a recipe for good government.