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For Eric Abetz, one of Tony Abbott’s most loyal supporters, it’s not over.

“I think Mr Abbott would be entitled to a cabinet position,” the conservative Liberal senator tells The Saturday Paper. “There’s no doubt Tony has a lot to contribute to public life and the public discourse in Australia and indeed the world, and I for one hope that he remains in the parliament.”

Abbott has deferred his decision on whether to stay in politics and it has become a central question of 2016, as he becomes the focal point for an insurgency that risks destabilising the Malcolm Turnbull-led Coalition.

Abetz says giving Abbott a cabinet role could help heal deep rifts in the party following the change in leaders in September and the reshuffle that saw the involuntary exit of some of the old guard, including Abetz and former defence minister Kevin Andrews.

“I think he would be well suited to serve in a range of portfolios but, importantly, I think the conservative voice deserves stronger representation around the cabinet table,” Abetz says in a provocative riposte to Turnbull. “The purge of the conservatives has diminished the voice of the rank and file in the Liberal Party.”

Abbott’s leadership has been the story of 2015. He started the year on the defensive, with 39 Liberal MPs backing a spill motion against him in February. After Abbott failed to revive the government’s ailing fortunes and continued to inflict own goals, Turnbull toppled him in September, 54 votes to 44. The Coalition had taken a leaf out of Labor’s playbook, axing a first-term PM.

“There’s this old guard, like Eric and Kevin, who think Tony’s redemption will be their redemption.”

Since then, Turnbull has turned around Labor’s poll lead and heads into an election year in a comfortable position, as opposition leader Bill Shorten’s personal approval ratings sink to new lows. Still, difficult decisions loom, as was evident this week when the Mid-Year Economic and Fiscal Outlook forecast ballooning deficits, delaying the return to a balanced budget until 2020-21 at the earliest.

Despite Turnbull’s strong polling, the party is still riven by bitter recriminations.

Turnbull and Abbott’s rivalry dates back decades and some of Abbott’s supporters are convinced this story still has a long way to run. Asked whether Abbott could one day regain the top job, Abetz implies this is possible, citing other dumped leaders who have mounted comebacks against the odds.

“In politics, you never say never,” Abetz says. “I can’t see it at this stage, but look, people said that about Robert Menzies, they said it about John Howard, they said it about Kevin Rudd, so it is a very brave person who makes those sort of predictions.”

Julia Gillard’s prime ministership was arguably not well served by the presence on her frontbench of Rudd, the leader she deposed. But Abetz says this is different. “Kevin Rudd was all about Kevin Rudd,” he says. “Tony Abbott is all about service to the community.”

Abetz’s call for the former PM to be given a cabinet position echoes the view of Abbott’s close friend Greg Sheridan, foreign editor of The Australian, who wrote last week that “the success of centre-right politics may yet depend on a reconciliation between Abbott and Turnbull”.

1 . Abbott's “noble calling”

As to what is going on in the mind of the former prime minister, his frequent media appearances in recent weeks give ample clues: he is vigorously defending his legacy and the performance of his controversial chief of staff, Peta Credlin, while also disputing accounts that he failed as leader.

“I think it was a very successful government in spite of a feckless senate, an irresponsible Labor Party, a poisonous media culture and well-organised white-anting,” Abbott told The Sydney Morning Herald’s Peter Hartcher earlier this month, while also disputing Julie Bishop’s version of the events surrounding his demise.

Another sign of the ongoing acrimony is that Credlin, following the leadership change, personally urged some Coalition staffers not to work for Turnbull.

Abbott is sending strong signals he intends to stay on, saying public life is a vocation and being a backbencher is a “noble and honourable calling”.

In domestic and international forums, the former prime minister is talking tough on national security, with comments about Islam that strike a much more strident tone than Turnbull’s.

In October, he used a speech in London to urge Europe to follow his government’s tough approach to refugees and ignore the Christian imperative to love your neighbour as you love yourself. “This wholesome instinct is leading much of Europe into catastrophic error,” he said.

Last week, in a speech in Singapore, he repeated his calls for Western troops on the ground in Syria and Iraq to end “the caliphate” of Daesh, a task he said could take decades.

Then, in an opinion piece in News Corp tabloids and an interview on Sky News last week, he called for a “religious revolution” inside Islam. “All cultures are not equal,” he said, “and, frankly, a culture that believes in decency and tolerance is much to be preferred to one which thinks that you can kill in the name of God, and we’ve got to be prepared to say that.”

This went too far even for some conservatives. Assistant Minister for Multicultural Affairs Concetta Fierravanti-Wells, a staunch right-winger, said the comments were simplistic and that practising “megaphone politics” was dangerous.

2 . Turnbull's strategy

Turnbull recently met with Abbott but, publicly, he has tried studiously to ignore his utterances.

This strategy reached its limits last week at a press conference in Perth, when the prime minister was repeatedly asked what he thought of Abbott’s comments about Islamic culture.

Turnbull replied that everything that he said, as prime minister, was based on advice from ASIO and the Australian Federal Police and was carefully calculated to make Australia safer. Then, after several questions on the subject, he snapped and declared: “Now, that’s enough on Mr Abbott.”

But the former prime minister’s supporters will not be silenced. The next day, Immigration Minister Peter Dutton pointedly defended Abbott. “He was very strong on national security when he was a prime minister and he’s continuing to have an interest in that area,” said Dutton, who some Abbott supporters argue should be made a permanent member of the national security committee of cabinet, which is now dominated by moderates.

Abetz nominates Abbott’s approach to national security as one of his strengths, saying his hard line on Russia – he threatened to “shirtfront” Vladimir Putin over the shooting down of civilian aircraft MH17 – and on border protection “shows strong, gutsy leadership that the world actually needs”.

Other Liberal MPs doubt Abbott could ever serve in a Turnbull cabinet and mock the suggestion he could be given cabinet responsibility for defence or counterterrorism, describing this as a dangerous proposition. But some in Abbott’s circle are still smarting from his ousting and are not intending to allow Turnbull a clear run as leader.

One Turnbull supporter says that Abbott, as a former prime minister, has the right to speak out and should be given time to decide on his future, but acknowledges that it’s a question that is dividing the party.

“There are some who say Tony should move on because everything he says is seen through the prism of Tony versus Malcolm and then there’s this old guard, like Eric and Kevin, who think Tony’s redemption will be their redemption,” says the Liberal source.

“You need to understand, it’s been a very traumatic year for some people and it’s going to take time for some of those wounds to get better.”

Another Liberal party source is less charitable about Abbott and his supporters, saying the social conservatives around the former PM are convinced of the righteousness of their mission, on topics such as same-sex marriage, but have failed to grasp that society has moved on. “Even the dinosaurs had the dignity to realise they were extinct,” says this source, who believes Turnbull’s prime ministership may rival Menzies for longevity.

At next year’s election, Abetz will contest another six-year senate term. Given he tops the Liberals’ ticket in Tasmania, he is certain to succeed. His own ambition to return to the frontbench is unlikely to abate. Andrews, who has in recent weeks called for Australia to send ground troops to fight Daesh, also intends to recontest his seat of Menzies. Abbott will make a guest appearance at a community morning tea in Andrews’ electorate on Saturday, amid claims that conservative branch members are furious he was toppled and are uneasy about Turnbull’s leadership.

3 . Backbenched former prime minister

Abbott himself is keeping his options open. He intends to at least serve out this term and will need to make up his mind about his future beyond that by the time preselections are called in his seat of Warringah, around March or April.

His supporters argue he is entitled to take his time with the decision. They point out that Turnbull, after losing the opposition leadership to Abbott in 2009, initially said he would not recontest but then changed his mind.

“I said back in mid-September that I would be talking to family, friends and trusted colleagues over the Christmas period and then I would resolve it,” Abbott said in an interview with Sky News presenter Paul Murray last week.

“I’ve got to say, Paul, that I’ve had literally thousands and thousands of messages of support and encouragement since mid-September. I’ve had a lot of people talk to me as I get around the electorate and still, to some extent, around the country, and the message I am getting from them, overwhelmingly, is that I still have a contribution to make to our public life. Now, I’m not going to, as it were, rush into a final decision; but that’s certainly the overwhelming message that I’m getting from people.”

If that sounds like someone who is keen to stay on, it should be noted that even some MPs who supported Abbott in the leadership contest wonder if he could be of more assistance to the Liberal cause from outside the parliament.

“He is a former prime minister,” says first-term Liberal MP Luke Howarth, who acknowledges he won his Brisbane-based seat of Petrie under Abbott’s leadership. “He doesn’t have to be in parliament to help our side of politics. He can mentor people and help our candidates coming through. Maybe he will contribute even more when he leaves parliament.”

Howarth’s Parliament House office is near the former PM’s new backbench suite: he’s observed that Abbott is enjoying spending a lot more time on his bike. Howarth is a regular at the so-called “monkey-pod” lunches where conservative Liberals, including Abbott, gather on Tuesdays of sitting weeks. He scoffs at media reports suggesting these lunches are anything other than a convivial gathering for Chinese takeaway.

“I guess you can’t change leaders and expect the previous leader to stay quiet if he’s still in parliament,” says Howarth, who is aiming to lift his wafer-thin margin to 5 per cent at next year’s election. “But everyone in the Coalition is behind Malcolm Turnbull now.”

Liberal backbencher Dennis Jensen, who played a role in bringing on the February spill motion, says it’s up to Abbott to decide on his future but adds: “I think he’ll find it a bit demoralising sitting on the backbench”.

Abbott is discovering what other leaders before him have learnt: it is not necessarily easy for former prime ministers to walk into corporate roles. Soundings have been taken by Liberal figures in the business world but no job has yet been found.

Turnbull, who knows from personal experience how gutting it is to lose the leadership, may well be hoping that Abbott finds another “noble and honourable calling” beyond parliament and does not follow his example and choose to stay.

Otherwise, the age of Turnbull may be undermined by echoes of the age of Abbott.