Peter Duncan, one-time figurehead of SA Labor’s now-marginalised hard Left faction, once known as the ‘Duncan Left’, insists major party insiders will be “seriously considering an across-the-board preference swap between them to cut the head off the Xenophon snake”.

In a Facebook post seen by InDaily, Duncan – a former Attorney-General and Health Minister in the Dunstan and Corcoran state governments and Employment Minister in the Hawke Government – said while such a move would incite an electoral backlash, and a jump in Xenophon’s support, it would “not be sufficient for his party to win a bag of seats against a Liberal/Labor preference deal”.

The post reveals Duncan first predicted Xenophon would make a run for state parliament in April last year – six months before he shocked the political scene with his announcement he would quit the senate to contest for the House of Assembly.

Peter Duncan in Adelaide in 2007. Photo: Todd Cardy / AAP

Duncan wrote at the time the Liberals would be “sufficiently desperate to get onto ministerial salaries [that they] might just agree to go into coalition with Mr X as the Premier”.

“Yes, I know he would have to resign from the Senate and run and win a lower house seat… however none of that is impossible,” Duncan predicted.

There’s only one reason why people like him would want to be in the Lower House – and that’s to be the Premier

In yesterday’s post, he offered two further predictions: that the major parties would seriously consider a “gang-up” deal to quell the “juggernaut”, with recent polls putting SA Best ahead of both Liberal and Labor both statewide and in key seats; and that Xenophon would “engineer the defeat” of Liberal leader Steven Marshall in his Norwood-based Dunstan electorate, where he this week confirmed the candidacy of 27-year-old engineer Jack Noonan.

“This will leave the Liberals as a leaderless rump after the election and make it easier to get the Liberal rump to support him as Premier,” Duncan wrote.

“The ‘Tiser [NewsCorp-owned Advertiser] is of course supporting him as positive payback for the X team supporting the Murdoch sponsored media bill in the senate.”

Sources have told InDaily there have been no formal conversations between the two major parties about preference arrangements, with both suggesting an across the board deal was highly unlikely – although it has not been ruled out and leaves open the prospect of preference arrangements in individual seats.

Xenophon told InDaily today it would be “unprecedented that Labor and Liberal would preference each other instead of a party from the political centre”.

“It would be an act of cynical bastardry that voters would see through in no time,” he said.

But former ALP senator and centre-left powerbroker Chris Schacht believes a “gang-up” preference deal against SA Best would never fly because “the membership would revolt and the voters would revolt”.

“It’s exactly what Xenophon wants,” he said.

“It would be impossible to do a deal like that, because your own voters – on both sides – won’t follow it, and it would be a gift to Xenophon for the next six weeks.”

He pointed to a disastrous historical preference deal against another former Attorney-General – Robin Millhouse – which saw the Labor vote collapse in Mitcham after the party put the Liberal-turned-Democrat behind the Liberal Party on its How-To-Vote cards.

Xenophon says he believes “fewer people are following How To Vote cards” in any case.

“I think people don’t follow How To Vote cards as much as they did,” he said.

There is data to bear this out. Results from the Australian Election Study, a routine survey of trends in Australian political opinion conducted nationally after each election, show a marked decline in respondents following How to Vote cards – likely mirroring a broader disaffection with the major parties – from 56 per cent in 1996, to 53 per cent at the 2004 poll – down to 43 per cent in 2013 and 34 per cent in 2016.

Nonetheless, in tight seats – as many will be – more than a third of voters directing preferences as instructed will still make a material impact. SA Best’s electoral gains are likely to come in seats where the party finishes second on primaries – but ends up ahead on a two-party-preferred basis after the distribution of preferences. However, a recent YouGov Galaxy poll conducted for Andrew ‘Twiggy” Forrest’s philanthropic Minderoo Foundation found SA Best leading the race on primaries in three key seats – including Xenophon’s own target seat of Hartley.

Contacted by InDaily, Duncan – who now resides mostly in Indonesia – said he made a general point not to publicly weigh in on political issues, but was happy to discuss the issues raised in his social media post.

“I just can’t believe the media commentators haven’t seriously picked up on the fact [Xenophon] nominated for the Lower House, and not the Upper House,” he said.

“There’s only one reason why people like him would want to be in the Lower House – and that’s to be the Premier, because you can’t be the Premier from the Upper House.

“The reality is he’ll end up as the dog wagging the Liberal tail – that’s the most likely scenario and I think that’s the one he’s counting on…

“The best position for him to negotiate that would be with a leaderless Liberal Party… and that presumably means doing something special in Dunstan.”