What happens to centre-right politics if One Nation continues to grow?

Some people have asked me why the fascination with One Nation in South Australia – after all they have only won one seat at the moment?

That might be true, but if I'm reading the tea leaves correctly, they boosted Labor's 2PP margin by around five percentage points and delivered them 68 per cent of the seats on a notional two-party-preferred of about 60 per cent.

In other words, One Nation are currently kryptonite to the chances of centre-right governments.

Then there is the fact that the Liberal Party, which has been the dominant party in Australia for almost 80 years, came in third on first preferences after Labor and One Nation, with One Nation finishing in the top two in around half the seats.

At the moment it looks like the best the Liberal Party can do is win nine seats. One Nation might win up to six, although some of those are Liberal v One Nation contests, so it's even possible – on their best result – that it ends up six all.

One Nation will also win three Legislative Council seats, the same as the Liberals.

While the overall first preference swing was clearly to One Nation, there were swings in all directions – both for and against Labor, and for and against the Liberals.

There may have been a net gain to Labor of around five seats, but that includes losses, and some surprisingly large swings. While Waite swung 18.3 per cent to Labor, Elizabeth swung 16.2 per cent against. That suggests a social realignment occurring under the surface.

There is a theory that if only the Liberal Party would move to the right they would start winning elections. This election provides evidence against that. While One Nation did well, it didn't expand the non-Labor vote, and the state remains decidedly left-leaning.

In fact, before One Nation's rise in the polling Labor was sitting on around 38 per cent first preference and a 2PP of about 54 per cent. After One Nation's surge the primary held, but the 2PP lifted to around 60 per cent.

Quick and dirty analysis portrays the rise in One Nation as a defection from the Liberals, but voters were moving in all directions. Some Liberals moved to Labor as well as to One Nation, while Labor voters also moved to One Nation and the Liberals.

There is a 'purity/disgust' element to voting for One Nation. The party has been so heavily demonised that some respectable people cannot countenance ever voting for it. Respectable people often vote Liberal and identify as moderates.