After December’s Newspoll suggested SA Best was outgunning both major parties on the primary vote, Xenophon swiftly lifted his sights – his original ambition to contest around a dozen Lower House seats soon became 20, then 24 (the number required to form a majority in the 47-seat parliament), then 30, before finally running out of steam at 36.

All of which had plenty of pundits, including within major party ranks, fervently predicting he could finish up with more seats than the Liberal Party, whose terrain he appeared set to plunder – particularly in the Hills seats nestled within the footprint of the federal Mayo electorate, where the NXT’s Rebekha Sharkie was already ensconced.

In truth, before the campaign proper had even begun, this scenario had all but evaporated.

The prognostications of SA Best’s success were always based on one fundamental assumption: that the party had enough residual appeal to run second on primaries in a significant bloc of seats, and would surf into first place on preferences.

Thus, Labor’s unprecedented decision to split its preferences 50/50 between the Liberals and SA Best effectively locked Xenophon out of the state election.

While we’re yet see to the specifics of the strategy, Labor declared they would run a split ticket in Hartley, where the SA Best leader himself is running, and preference the Libs ahead of his party in 23 of the remaining 46 seats.

Remember, of course, that Xenophon is only running 36 candidates in total. So, in other words, based on Labor’s original stated intent, SA Best wouldn’t get Labor preferences in around two thirds of the seats it’s contesting.

On Tuesday, however, state secretary Reggie Martin clarified that because Xenophon was only running candidates in 36 seats, rather than all 47, Labor would in fact only preference against SA Best in half the seats it’s contesting – rather than half the seats in total.

But that’s still 17 or 18 seats in which SA Best can’t rely on Labor preferences.

The question is: do Labor and the Libs do a trade-off deal to safeguard their respective heartland seats from the Xenophon threat, with half an eye on the election in 2022, and the one after that?

History suggests that once an independent or third-party interloper gets a foothold in a disaffected electorate, they can be hard to shift. And while both Labor and Liberal parties are desperately trying to win government on March 17, neither side wants to be dealing with a gaggle of entrenched SA Best refugees in the longer term.

A preference ‘lock-out’, which has had vocal support from advocates on both sides, would effectively negate the entire premise of this campaign: that Xenophon can rely on preference flows to translate his protest vote into a genuine power play.

But the last week and a bit has thrown up an even bigger impediment to his quest.

December’s Newspoll was followed in late January by a leaked YouGov Galaxy poll commissioned by Xenophon-friendly entrepreneur Andrew ‘Twiggy’ Forrest’s Minderoo Foundation, which showed SA Best on the way to solid wins in both Hartley and Mawson, as well as being a mile ahead in Mayo.

But a succession of subsequent polls, including an Australian Forest Products Association-backed Reachtel poll in the state’s south-east and most recently a series of Advertiser-Galaxy snapshots in key seats, suggests the gloss is well and truly coming off Xenophon’s campaign.

Of biggest concern to Xenophon will be yesterday’s poll in Isobel Redmond’s former seat of Heysen, which showed SA Best’s John Illingworth trailing Liberal hopeful Josh Teague 39-22 on primaries and 51-49 after a speculative preference throw.

Sure, it’s lineball – but at the 2016 federal election, Sharkie actually won the primary vote in the booths that make up Heysen, 6309 votes to the Libs’ 5954. It was the only seat in the state in which a projection of the federal election results had Xenophon’s party actually finishing first on primaries, rather than second.

Indeed, senior Liberals had already effectively written it off and were doing their best to wash their hands of the local campaign.

Steven Marshall with fellow moderate, Heysen candidate Josh Teague.

But now it’s not only in play, it’s the Libs’ to lose.

As the campaign wears on, a nagging suggestion appears to gain currency: that NXT’s success in the Hills region was artificially inflated by an unrelated backlash against the Liberals’ former Mayo MP, Jamie Briggs. And if so, the very premise upon which Xenophon embarked on this entire enterprise – that seats such as Heysen, Finniss, Morialta, Davenport and Kavel are all-but his for the taking – appears to have been vastly overstated.

To be clear: if Xenophon cannot snare seats such as Heysen, it’s entirely possible he will snare no seats at all.

Tom Richardson is a senior reporter at InDaily. Read the read of this article here.