Rarely – perhaps never – has the winner of an election felt more like a subplot to a bigger and more consequential narrative than in South Australia on Saturday night.

The ABC called the result for Peter Malinauskas and his Labor government less than 90 minutes after the polls closed, validating the opinion polls that had long forecast a landslide victory.

But it was the trail of political carnage and upheaval left behind them that will prove the bigger story in SA and beyond.

The election was billed as the first test of whether an insurgent One Nation could translate support in opinion polls into votes at the ballot box – and what that would mean primarily for the Liberals but also for Labor.

With 30% of the vote counted on Saturday night, One Nation was polling 21.1% of the primary vote – ahead of the Liberals.

The biggest swings were in the regions, where it is a threat in several once-safe Liberal seats including Chaffey and Hammond and the independent-held Narungga.

Even if none of those turn orange, One Nation will have a significant presence in the SA parliament with Cory Bernardi, state president Carlos Quaremba and possibly one other set to win seats in the upper house.

As One Nation eroded the Liberal vote in the bush, Labor marched further into blue territory in the city, flipping the metropolitan seats of Colton, Hartley, Morialta and Unley.

The political pincer movement – which might leave Ashton Hurn’s Liberals with just four or five seats when the counted is completed – is a microcosm of the predicament the party faces nationally.

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One Nation has also taken skin off the government in working-class suburban seats such as Elizabeth in Adelaide’s north and Kaurna, south of the city, proving that Pauline Hanson’s brand of rightwing populism is also attracting Labor voters.

If Saturday night was a litmus test, One Nation passed.

The results will be picked apart over coming days and assessed for potential federal implications.

Mercifully for the federal opposition leader, Angus Taylor, it would be foolish to expect what occurred on Saturday could be neatly extrapolated to the federal sphere.

Malinauskas is a uniquely skilled politician and far more popular than the prime minister, Anthony Albanese.

Equally, the SA Liberals are a uniquely dysfunctional political outfit – its turnstile of leadership over the past four years make its counterparts in Canberra appear stable in comparison.

But Taylor and Albanese would be naive to think there aren’t clear danger signs for them.

There is now verifiable proof that Hanson has broken into the mainstream, harnessing a deep distrust and discontent with the political establishment that could worsen amid skyrocketing fuel prices and rising interest rates.

Hanson said she felt “vindicated” by Saturday night’s result, which will generate momentum for One Nation before the 3 May Farrer byelection and November’s Victorian election.

The question now, for the major parties, is how to respond.

The major parties are right to call out Hanson for her comments on Muslims and other communities and the manner in which she preys on grievance, offering hollow solutions to the real and complex problems faced by many Australians.

But the politicians would be gravely mistaken if they believed the grievance wasn’t there – or misunderstood what was fuelling it.

It is on this point that Malinauskas offers the most useful template for combatting One Nation.

The Labor premier didn’t dismiss or downplay the grievance during the campaign, arguing it was born of a legitimate sense of “lost opportunity” – in particular on housing.

The role of parties of government, he argued, was to devise and deliver policies that actually fixed the problems.

Fiddling at the edges might longer be enough.

Because something has changed in Australian politics.