Ousted PM Malcolm Turnbull has, true to his word, cursed the “insurgents” in his party with a potentially debilitating by-election battle.

The Member for Wentworth will be member no more by the end of the week. He will write to constituents explaining his decision on Tuesday, the ABC and Nine News reported.

Because the next election is thought to be months away, this sets up a dangerous contest to replace him.

The immediate problem for the government is that when Parliament returns on September 10, the Coalition will have lost its one-seat majority. Winning a Labor-induced vote of no confidence could prove difficult – though not impossible if the crossbench co-operates.

While a safe seat, Wentworth has not always been the extreme ‘blue ribbon’ it became under Mr Turnbull.

He easily won with a margin of 15 per cent or more in 2010, 2013 and 2016. But the margins had been much slimmer: just 3.85 per cent in 2007 and 2.51 per cent in 2004.

It is an affluent and socially progressive electorate. Just over 80 per cent of Wentworth voters supported same-sex marriage in the recent postal survey, the fourth-highest ‘Yes’ vote in the nation.

For this reason, candidate selection may prove crucial.

Tony Abbott’s sister, Christine Forster – a key supporter of same-sex marriage – has already nominated.

And Mr Turnbull’s son-in-law, James Brown, the RSL NSW president, appeared to leave open a run.

“There has been some speculation that I will enter federal politics. Let me be clear: I am fully engaged in the task of returning this league to be the pre-eminent organisation caring for veterans and their families,” Mr Brown said in recent days. It was no outright denial.

The frontrunner candidate is reportedly Dave Sharma, the former Australian ambassador to Israel.

The chaos that brought down Mr Turnbull won’t make winning the seat any easier for the Liberals, with the latest Newspoll putting the government’s primary vote at a crippling 33 per cent nationally. If accurate, this would result in about 21 lost seats.

Also problematic is the fact that the party’s coffers are depleted, as more than one party figure has admitted publicly. It could prove difficult to match a heavily-funded Labor campaign.

The Wentworth by-election is not the only revenge wrought by the Turnbull family.

The former PM’s son, Alex, a fund manager based in Singapore, has in recent days blasted the conservative forces that overthrew his father.

When Newspoll dropped, he described the result on social media as the “ouroboros of Australian rwnjs”, a reference to a dragon eating its tail. ‘RWNJs’ stands for ‘right-wing nut jobs’.

And there was more.

“The extreme right of Australian politics doesn’t really seem to have coherent objectives at all,” he said, responding to a video released by the Institute of Public Affairs.

Alex Turnbull fired a salvo at the boss of News Corp too, perhaps indicative of an opinion widely held in the family.

“Tough times Rupert Murdoch,” he wrote, referring to Peter Dutton’s failure to seize the prime ministership.

“An ex of your wife wrote a great tune about times like this. I think it was played at a recent inauguration, can’t remember which.”

Alex included a link to You Can’t Always Get What You Want by The Rolling Stones. Mr Murdoch’s wife, Jerry Hall, was a long-time partner of Stones frontman Mick Jagger.

Meanwhile, one of the men chiefly responsible for the coup, Tony Abbott, insists he is going nowhere. He confirmed on Monday he would contest the next election.

The moderates, and some conservatives too, who lined up to slam Mr Abbott in Monday night’s episode of Four Corners may well believe the wrong man is leaving Parliament.

Even Senator Concetta Fierravanti-Wells, a Dutton backer and key conservative, admitted Mr Abbott had “unresolved issues” after losing the leadership and was “very active in maintaining a degree of agitation about his position”.

“For Tony, this is unfinished business and he’s got his agenda.”

