Western Australia senior Liberal Michaelia Cash gave her backing to the shortlist changes, saying the party must reform or pay the price.
Senator Cash issued the warning after the opening of the WA Liberals State Conference in Perth on Saturday.
Participants are asked to support a motion to have lower house MPs pre-selected by plebiscite of party members in each electorate.
The proposal, led by party chairman Richard Wilson, is expected to be debated on Saturday afternoon.
It comes after the Liberals suffered a 10% swing in WA in the federal election, losing five seats as Labor claimed a majority government.
In last year’s state elections, the party was whittled down to just two lower house lawmakers amid internal unrest over alleged branch stacking and factional control of shortlists.
Senator Cash said she was confident members of the warring parties would put aside their differences and support the proposed change.
“I think the people of Western Australia have given us a very, very clear message: reform or pay the price,” she told reporters.
“We need to give every member of the Liberal Party in every division the opportunity to have a say.
“We will get there today, I hope.”
The motion needs the support of 75% of conference attendees to pass.
Former head of state Mike Nahan and other party elders will propose amendments against the proposed plebiscite model, arguing that it should also include upper house screening and exclude delegates who do not live locally.
Senator Cash confirmed that she would support the amendments, but said the reform should still be pursued even in its current form.
Dr Nahan said the chair’s proposal had flaws but did not rule out backing it if the proposed amendments fail.
He told AAP it was “ridiculous” that the party had more branches now than 30 years ago despite a drop in membership.
“It’s going to be tight,” he said of the vote on the amendment.
“Our major problem is that the vast majority of our branches are extinct, non-existent, controlled by a small group of people.
“If the president stands up and says ‘this is step one of reform’…then I think most of us could live with it.”
Conservative eminence and upper house MP Nick Goiran said he would support the president’s proposal, but declined to comment on the proposed amendments.
He denied that the party had struggled to attract high-quality candidates.
A damning review last year found that the WA Liberal Party had become a political “wasteland”, in part because of the corrosive influence of factions.
The report says the party’s financial viability is threatened by an exodus of corporate funding.
“If our situation does not lead to new reforms, we are doomed,” said Dr Nahan.
In the absence of Federal Leader Peter Dutton, his deputy Sussan Ley told members she was confident the Liberals could be re-elected in 2025.
She said the party had been deregistered before “and every time we come back to government”.