Ms Allan is refusing to step down after a cross-factional delegation, including six ministers, informed the embattled leader she had lost majority support of the caucus.
A leadership spill motion is expected to be put to the caucus on Tuesday morning which, if successful, could pave the way for a potential leadership contest just four months out from the election.
Ms Allan, from the party's left faction, flagged her intention to nominate for the leadership if it goes to an internal vote.
Deputy Premier and Education Minister Ben Carroll confirmed he will throw his hat into the ring.
Mr Carroll, from the party's smaller right faction, was swarmed by media as he exited a car and entered parliament through a side door.
"Right now my focus is on talking to my colleagues and I will have more to say later," he said on Tuesday.
Attorney-General Sonya Kilkenny would not be drawn on whether the party's left faction would run another candidate in the event of a leadership contest with Mr Carroll.
"I'm here today as minister of this government and the premier has my support," she said.
Economic Growth and Jobs Minister Steve Dimopoulos, considered another potential leadership candidate, said Ms Allan had "always had his support".Â
"I'm going to respect the process," he said.
Outgoing Labor MP Mary-Anne Thomas also professed her loyalty to the premier, whom she described as a close friend.
Federal Foreign Minister Penny Wong said politics was a tough game and good people had to do "difficult things" at times.
"I will leave it to them to resolve," she told ABC TV.
"Obviously, whatever the outcome, we will be working with them in the lead-up to state election."
If the leadership challenge eventuates, caucus and rank-and-file party members will vote for their preferred leader in a weeks-long process.
A caretaker premier, who is not a nominee, would need to step in to lead the party during that time.
Parliament is also set to debate an opposition no-confidence motion in the premier and government, which can trigger an early election in the unlikely event it passes.
"This is a unique opportunity for Labor members of parliament not to stab their boss in the back in a side room in parliament," Shadow Attorney-General James Newbury said.
There's no guarantee Mr Carroll can lead Labor to a record fourth-straight election victory if he were to become premier, Redbridge pollster and former Liberal strategist Tony Barry said.
A significant cabinet reshuffle and policy overhaul would be needed to differentiate Mr Carroll's politics from Ms Allan's and subsequently remedy the drop in voter support for Labor incurred under her leadership, Mr Barry said.
"There's going to have be changes around the Suburban Rail Loop and other things where he differentiates himself from Jacinta Allan," he said.
"Otherwise he's going to be completely open to the attack of same horse, different jockey.
"In that situation, he might make a bad situation even worse."
Labor's push to put the leadership to a vote has dealt Ms Allan's chances of leading the party at the election "a mortal blow", Mr Barry said.
Ms Allan has faced mounting pressure in recent months following revelations of corruption on Big Build projects.
She has refused to call a royal commission into the sector after corruption-busting lawyer Geoffrey Watson estimated it had cost the state $15 billion.
Persistent crime and a failure to reach a pay deal with public school teachers have also dogged the government.
6°C