Nick Xenophon has turned the 2018 state election into the most crucial South Australian political battle in a generation.

His bombshell announcement today that he is quitting the Senate in a bid to return to state parliament will reshape South Australian politics for the foreseeable future, with the Liberal Party facing an increasingly complicated and perilous path back into power.

Labor, which by any conventional analysis should be turfed out next March after 16 years in power, is now a better chance to squirm its way back onto the government benches, although there are no certainties in what will be a genuine three-way race in many seats.

As a key senator in the relentless spotlight of federal politics, Xenophon has been spread very thin, giving occasional hints that there was a mounting personal cost. His federal team has run relatively smoothly; it’s not hard to imagine the appeal of a renewed focus on local politics, despite the risks of looking flaky for jumping out, and back, into state parliament.

Xenophon will run for, and almost certainly win, the Liberal-held seat of Hartley, in Adelaide’s eastern suburbs – a swing seat in recent elections.

Polling data is sketchy, but Xenophon has consistently been rating at 20 per cent or above for state voting intentions. His dramatic decision to leave Canberra for his old North Terrace stomping ground will only increase his vote, raising the possibility of SA Best grabbing a clutch of seats. He clearly expects to hold the balance of power with his SA Best party – although, apart from his own candidacy, the rest of his team is yet to be confirmed.

Today’s announcement changes the political dynamics in profound ways, adding Xenophon’s personal authority to the SA Best brand.

The old attack line – that a vote for Nick is a vote for (insert name of major political party here) is now redundant, although that hasn’t stopped the Liberals already rolling it out again today.

Voters will figure that a vote for Nick is now, literally, a vote for Nick. Coverage of the election campaign will have a three-man focus: Jay Weatherill, Steven Marshall and Nick Xenophon.

Residual suspicions about the quality and reliability of Xenophon-branded state candidates can be mitigated. The man himself will be running the state show.

Labor and Liberal strategists will have to deal with this threat carefully and shrewdly, given that Xenophon himself will conceivably determine the flavour of the next State Government.

An outright attack on Xenophon’s credibility now comes with high risk for the major parties.

For the man himself, he now has a personal stake in negotiations, should he find himself as the kingmaker.

Xenophon has ruled out accepting any place in Cabinet – so what will he be? A pseudo-opposition leader? A cabinet minister without the title or responsibilities? The implications for the government – whoever that is – are mind-boggling.

Campaigning will now be a complex nightmare for the major parties, with the Liberals in particular facing a packed chequerboard of threats in some of their heartland seats, particularly in the Hills, and now in the eastern suburbs of Adelaide.

Anything is now possible, with the Senator not ruling out supporting either major party after the March poll.

His pitch will resonate with South Australian voters who, like their counterparts across the globe, are clearly fed up with business-as-usual politics.

But while the idea of Xenophon moderating the power of major parties in the parliament will be appealing to many voters, the longer-term consequences for Xenophon might be dangerous to his personal brand.

For the first time in his clever, populist political career, he faces the possibility of grasping real power – not just being a deal-maker in houses of review, but being at the centre of decision-making. South Australians should demand detailed policies and should hold him to his promises if he gains power (in whatever form that takes).

And, in that scenario, the rubber will hit the road.

Will he be revealed as a true game-changer, or just like every other politician?

Will realpolitik reveal the real Nick Xenophon?