The two main figures in Australia's July 2 election are Prime Minister Malcolm Turnbull and Opposition Leader Bill Shorten, but a third one is looming over the campaign.
Despite now being a backbencher, Mr Tony Abbott continues to command attention and poses an ever-present threat to Mr Turnbull, who deposed him in a Liberal Party leadership coup last September.
After his ouster, Mr Abbott opted to remain in politics and has since been "haunting" - as several commentators have put it - his old foe.
Mr Abbott has even begun to hint that he would like to return to the leadership.
While launching his campaign in his north Sydney constituency on May 15, he was greeted by a well- wisher who told him: "God willing, you will be prime minister again."
Smiling broadly, Mr Abbott, a devout Catholic, reportedly responded: "Let's see what the Lord has in store for me."
The former prime minister's lingering presence has been a constant disruption for Mr Turnbull's campaign.
Despite being publicly unpopular, Mr Abbott, a staunch conservative, retains strong support among a group of right-wing MPs in the Liberal Party.
He has become something of a figurehead for Liberal supporters who have been aggrieved by the rise of the more progressive Mr Turnbull to the leadership. Some in the party have been angered by Mr Turnbull's plans to lift retirement taxes on the wealthy and his failure to introduce big spending cuts.
Mr Abbott has insisted he will remain loyal and is "absolutely committed to the election of the Turnbull government".
But his presence is an unwanted distraction for Mr Turnbull, especially since both men know that the former leader could potentially derail his successor's campaign.
There is a recent - and brutally ugly - precedent for this in Australian politics. Five years before Mr Abbott was ousted, Labor prime minister Kevin Rudd was deposed in an equally brutal fashion by his deputy Julia Gillard. He stayed on as a backbencher and was allegedly the source of a series of damaging leaks to the media that severely affected her subsequent election campaign.
She lost her parliamentary majority in the 2010 election and was forced to make a deal with independent and Green MPs to cling on to power.
As observers have noted, Mr Abbott could easily conduct a Rudd- style sabotage.
"Whether intentionally or not, Abbott is haunting this election campaign as effectively as Kevin Rudd haunted Julia Gillard in 2010 and onwards," political commentator Jacqueline Maley wrote in The Sydney Morning Herald on May 21.
"He is just being smarter about it - more stealthy, more patient, more strategic, more arm's-length. And Turnbull is looking spooked."
Three years younger than his rival, the 58-year-old Mr Abbott may be biding his time and hoping that, if conditions suit, the party may demand his return as leader.
Commentator Troy Bramston said Mr Turnbull will face intense pressure on his leadership if he fails to win convincingly in July. If the party loses, he predicted that Mr Abbott could make a comeback.
"As Turnbull falters and conservatives revolt, a return to Abbott post- election cannot be ruled out," Mr Bramston wrote in The Australian on May 23. "Abbott, a rejected and dejected man only months ago, waits in the wings to be recalled to the political stage."
For now, Mr Abbott's return seems unlikely, as Mr Turnbull is expected to improve his position as the campaign continues and win the election. He also remains unpopular.
But Mr Abbott knows that some of his party's most successful leaders were reinstated after previously being considered politically finished, including Mr John Howard, who was prime minister from 1996 to 2007.
And he may be looking to an even more recent precedent: Labor's reinstatement of Mr Rudd as prime minister in 2013. It is worth recalling what happened next: Within months, Labor was soundly defeated at the polls and Mr Rudd resigned from Parliament. The winner of that election was Mr Abbott.
It remains to be seen whether Canberra's recent turbulent political history will repeat itself again.
