A vote to roll Ms Ley is widely expected during the Liberals' regular party room meeting when parliament returns on February 3.
Opposition defence spokesman Angus Taylor and opposition home affairs spokesman Andrew Hastie are seen as the frontrunners to replace her.
Ms Ley's critics accuse her of a failure of leadership: for demanding parliament be recalled following the Bondi terror attack, calling Labor's anti-hate legislation "unsalvageable" and then eventually supporting it.
But insiders are hesitant to move too quickly against Ms Ley for fear of being seen to have caved to Mr Littleproud's demand for a new Liberal leader.
After blowing up the political alliance between the Liberals and Nationals on Thursday morning, Mr Littleproud said he would not return to the coalition while Ms Ley was leader.
"Remaining in a coalition with the Liberal party under the leadership of Sussan Ley has become untenable and cannot continue ... Sussan Ley has put protecting her own leadership ahead of maintaining the coalition," he said in a statement.
That sparked white-hot fury among Liberals, who see the comments as Mr Littleproud intervening in internal Liberal politics.
"The second he doesn't get what he wants, he throws a tantrum," one Liberal said of the Nationals leader.
Party sources, speaking on the condition of anonymity, said while they wanted Ms Ley gone, they were hesitant to give Mr Littleproud what he had demanded.
The anger is ultimately unlikely to deter Liberals from replacing their leader, but has made the calculus more complex, particularly for Mr Taylor, who insiders say wants to avoid blood on his hands.
The opposition defence spokesman has been holidaying in Europe, avoiding becoming embroiled in much of the drama playing out in Canberra during an emergency sitting of parliament on Monday and Tuesday.
Mr Hastie, who is based in Western Australia and has young children, must also decide whether he's prepared to embrace the hectic travel schedule of a party leader.
Moderate Melbourne MP Tim Wilson is also believed to be considering a tilt for either the leader or deputy position.
AAP has been told contenders are holding conversations to gauge support in the party room.
Ms Ley has remained defiant, despite the flood of criticism.
Asked on Thursday if she would survive as opposition leader, she said she would.
Liberals also said Nationals leader David Littleproud might need to be axed to provide a "reset" and allow the two coalition parties to reunite.
