Peter Malinauskas is heading for a landslide win in SA. How crushing a victory will it be?

Some elections are nailbiters, with fierce campaigns and scrappy seat-by-seat contests for votes.

South Australia has had its fair share of that kind of campaign, including when former Labor premier Mike Rann scraped over the line with independent support in 2002, or when his successor Jay Weatherill won the election no one expected him to win in 2014.

Unlike Rann and Weatherill, we're not expecting Peter Malinauskas to be sweating on the result for too long come March 21.

With the polls the way they are, and a distinct lack of state Liberals expressing any real hope of a good result, it seems safe to say that he will still be premier after this campaign is over.

The more interesting question is, just how big will Labor's win be?

Nationally, much of the attention will be on the undercard fight between the Liberal Party and One Nation, and that's where we might see some nailbiters.

Will the Liberal Party suffer merely a bad loss to Labor, or will it be a crushing defeat that all but wipes out the party?

And can One Nation demonstrate that it has become a real electoral force in Australia?

Even if the overall outcome is a foregone conclusion, the campaign that plays out over the next four weeks will still be a fascinating one to watch, and it will serve as a crucial pointer that might give us some hints about where politics nationally is heading.

Let's step through the three main battlefronts.

Labor's Adelaide offensive

Government in South Australia is won and lost in the suburbs of Adelaide, and a look at the map shows you why the Liberal Party is in so much trouble.

The opposition holds two seats by the beach, and a handful in the eastern suburbs.

Four years ago, Labor picked up seats further up the pendulum than was expected, including Waite, in the southern suburbs, and Davenport further south.

It also took a big chunk out of the margin of the other Liberal seats, meaning nearly all the opposition's Adelaide seats are now marginal.

A uniform statewide swing of six per cent toward Labor (which happens to be the estimated swing in this month's Fox and Hedgehog poll) would see the Liberals lose everything in metropolitan Adelaide except Bragg.

So Labor has its eyes on seats like Colton by the beach, where the Liberals are without the profile of Paralympian Matt Cowdrey who is retiring at this election.

In the eastern suburbs, the Liberals are defending Morialta, one of its most marginal seats, without former education minister John Gardner, who is also retiring.

The former opposition leader Vincent Tarzia could be in real strife in the neighbouring seat of Hartley.

And just south of the Adelaide CBD is the seat of Unley, which Labor hasn't won since the 1980s. It currently sits on a margin of 2.2 per cent, and the Liberals have another retiring member there, with David Pisoni stepping down.

In 2022, Pisoni's margin of victory was around 1,000 votes.

SA Labor has, in part, held on to power for 20 of the past 24 years in thanks to its exceptional marginal seat campaigning and tight discipline among its ranks.

The SA Liberal Party, by comparison, has been far more of a rabble, and has just been through a torrid four years.

If the party under Ashton Hurn, its third leader in this term of parliament, goes significantly backwards in Adelaide, it could raise existential questions about the future of the opposition.

The regional rebellion

The big threat in the city is Labor, but the Liberals face a second major threat in regional South Australia.

An independent who performed well in Finniss four years ago is having a second crack, and in Flinders, where another independent came within three per cent of victory, there's already a crowded field of candidates.

The opposition is also trying to win back the former blue-ribbon seats of Mount Gambier, now vacant after the imprisonment and resignation of former MP Troy Bell, Kavel, where Dan Cregan is retiring, and MacKillop, where the Liberal-turned-independent Nick McBride is campaigning while on home detention bail, facing domestic violence charges.

Those three seats are all notionally Liberal based on the results of the last election, but there are credible independent candidates in all three, and Liberal victory is far from assured.

The fact that the three incumbent members in those seats are all former Liberals further highlights the recruitment and retention problem the opposition needs to fix. 

Why would a promising young Liberal, looking at the prospect of years more in opposition and continuing internal tensions, seek to run for state parliament?

The X Factor, 2026 edition

Finally, the third big battlefront.

Eight years ago, politics-as-usual in South Australia was up-ended by an upstart party, surging in support, led by a popular political figurehead.

Nick Xenophon quit his position in the federal Senate to field a team of candidates in the 2018 state election, aiming to hold the balance of power in parliament.

After very strong initial polls, Xenophon's campaign struggled, the two major parties both campaigned against him, and his party's support fell during the campaign.

The party didn't win any lower house seats but elected two members to the Legislative Council (one of those, Frank Pangallo, is now the Liberal Party's candidate for Waite).

The Xenophon intervention in state politics, which occupied much attention and consternation ahead of the 2018 election, is now looked back on as a bit of a flop.

Eight years later, and politics-as-usual is now being up-ended by an upstart party, surging in support, led by a popular political figurehead.

This time, however, that figurehead is a Queenslander: Pauline Hanson.

This election is the first to be held anywhere in Australia since the marked surge in One Nation support that has occurred since last year's federal election.

Three polls of state voting intention published this month have all recorded a similar surge, and in all three cases, One Nation has higher first preference support than the Liberals.

Those figures are a nightmare scenario for the Liberal Party, and raise serious questions about whether it will remain a viable opposition.

One Nation is, perhaps wisely, not talking up the prospects of winning lower house seats. But this election is a big test for the party: can it maintain its strong support in opinion polls throughout an election campaign, and then convert that into strong support in the form of actual votes?

If it does, in which seats will those votes be? It's possible we could see One Nation overtake the Liberal Party to come in second place in a swathe of safe Labor seats. If that happens, it would be a big psychological blow for the opposition.

The result will give us an early sense of whether One Nation has a chance of becoming an entrenched force in Australian politics, or if we'll later be viewing it as a blip in time like the 'Xenophon for Premier' campaign.

The South Australian election brings strong parallels to the predicament facing the opposition federally: a conservative vote that is fracturing, independents and a surging One Nation trying to capitalise on that, and a Labor Party growing increasingly dominant in the urban centres.

In all directions the squeeze is on the Liberal Party, not Labor.

So while Peter Malinauskas is on track for a handsome victory, come election night, a lot of people are going to be poring over the performance of everyone else.

Read Chief Election Analyst Casey Briggs' election preview .