Sussan Ley’s leadership of the Liberal party is all but over, senior colleagues believe, after a spectacular split over hate speech laws blew up the Coalition for the second time in eight months.

Angus Taylor and Andrew Hastie were the leading contenders to replace her, according to multiple sources who anticipate a challenge could begin to materialise as early as Friday, following the day of mourning for the Bondi massacre.

Tim Wilson and Ted O’Brien have been mentioned internally, but were considered to be outsiders.

A special meeting to consider a leadership spill can be held if two MPs petition the party whip.

Two sources expected a petition for a spill could be signed over the next 48 hours.

Senior Coalition sources also believe David Littleproud’s leadership of the Nationals could also end, in an extraordinary post-script to a split over the Albanese government’s hate speech laws.

Littleproud on Thursday morning said the Coalition was “untenable” after Ley sacked three Nationals senators for crossing the floor over the laws, prompting all of the country party’s frontbenchers – including the leader – to quit the shadow ministry in solidarity.

He had earlier warned Ley about the prospect of a mass walkout of the shadow cabinet if she accepted the resignations of senators Bridget McKenzie, Ross Cadell and Susan McDonald, which she did on the grounds that shadow cabinet solidarity was non-negotiable.

‘You can’t come back from this’

Senior Liberals across factions believed the latest breakup meant Ley’s position was terminal, and comes after poor polling and a previous Coalition split.

“You can’t come back from this – it’s done and dusted,” one Liberal said.

Another Liberal MP described Ley’s position as “untenable” after the second Coalition split under her watch. “It is not salvageable in any way, shape or form,” they said.

One Liberal MP said Ley’s position was “extremely difficult going forward”.

“She will have to fight now,” they said.

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Guardian Australia spoke to more than dozen MPs about her future, and nearly all of them believe her time as leader was up – although the timing of any challenge and the likely successor are unclear.

Hastie and Taylor belong to the same right faction, meaning only one could realistically contest a ballot.

Sources said the pair needed to sort it out among themselves, allowing MPs to rally around one candidate who could then re-unite the Coalition.

Taylor was on Thursday reportedly planning to return from overseas, after missing this week’s special parliamentary sitting to pass hate speech and gun laws.

Wilson would hope to have support from moderate MPs if Ley stepped aside.

O’Brien, who is factionally unaligned, has a less clear path to the top job. One Liberal suggested he could be a “compromise” candidate, similar to Scott Morrison after the ousting of Malcolm Turnbull in 2018.

But frontbencher Melissa McIntosh urged the Coalition to stay together, saying the country needed strong leadership from the opposition “more than ever”.

“Our country needs the hope that we bring in the cities, the suburbs and the regions,” she said on social media.

The party room is next scheduled to meet when parliament returns on 3 February.

Some Liberals warned of the risk of allowing the Nationals to dictate the Liberal party leadership.

“If we decide to change our leader now, we’re caving into the demands of the Nationals again, I’m not up for that,” one Liberal MP said.

Another said that Ley could remain leader “if cooler heads prevail” over the coming weeks, but warned “once the fuse is lit, it’s hard to extinguish”.

One moderate Liberal MP said an immediate challenge would be reckless.

But others said a leadership change must be done quickly to avoid inflicting further damage.

“The problem for any conservative candidate is they can’t say convincingly they will be able to bring the Coalition back together, and they will struggle for credibility if they roll Sussan.”

One frontbencher said MPs were speaking about the party’s state of play, but sought to temper expectations about an imminent challenge.

Speaking on Thursday, Littleproud said he had tried to engage in “good faith”, but blamed Ley for accepting the resignations.

Ley released a statement shortly after Littleproud’s press conference, calling for focus to remain on the day of mourning for the victims of the Bondi terror attack.

“Today the focus must be on Jewish Australians, indeed all Australians, as we mourn the victims of the Bondi terrorist attack,” she said.

“This is a national day of mourning and my responsibility as leader of the opposition and leader of the Liberal arty is to Australians in mourning.”

Guardian Australia understands Ley asked Littleproud to delay media appearances until after the day of mourning.