Since announcing he would leave the Senate to run in the South Australian election, all eyes have been on Nick Xenophon and his SA Best candidates.

So far he's announced 26 people running for the Lower House, a number tipped to hit 30 within the next week.

That outweighs what's known as the "magic number" of 24, the figure a party needs to reach to form government.

But, even without 24 seats he could still become premier.

Here's how.

So, how does the magic number of 24 work?

There are 47 seats in South Australia's House of Assembly so any party that secures 24 seats forms government.

With polls putting the former senator and his party ahead of the major parties, and 26 candidates in the race, it's a very real possibility that SA Best could win government outright.

What if he doesn't win 24?

It doesn't take him out of contention for the top job.

If no party wins 24 seats, governing boils down to deal making.

Any party wanting to put forward a premier needs to convince the Governor that they could survive a "no confidence" vote in parliament.

That means, like many state and federal governments before, the major parties will have to negotiate with the crossbench for support.

If Mr Xenophon won fewer than 24 seats, but more than at least one of the major parties, he could be in a position to negotiate with the major party which finishes third to get to 24 seats.

For example, if SA Best won 16 seats, and the Liberal Party won 10, he could negotiate a deal with the Liberals to become premier.

There's also the possibility that SA Best finishes third, and premiership could become a pawn in negotiations to form government.

That is, SA Best could demand the top job in return for supporting one of the major parties to form government.

How likely is a future Premier Xenophon ... seriously?

While it's all hypothetically possible, according to ABC election analyst Antony Green, it's not probable.

Despite the polls, Mr Green said the most likely scenario is SA Best coming third in the three-horse race.

"He's not going to get a majority in his own right," he said.

"If he's going to form part of a coalition or be involved in some form of government, he'd have to win more seats than whichever party he chose to govern with.

"I'm not convinced he'll win more seats than Labor or Liberal."

Just who could be premier after the next South Australian election? ( ABC News )

He pointed to the experience of One Nation in Queensland, where the party polled well but only won one seat.

"[SA Best is] less likely to finish first in any electorate," he said.

"They're much more likely to finish second everywhere and then it's much harder for them to win.

"That was exactly the experience of One Nation in Queensland.

"They did impressively in lots of areas but they finished second everywhere and they didn't win seats as a result."

If there's no clear winner, what happens next?

If current Premier Jay Weatherill, Opposition Leader Steven Marshall and Mr Xenophon struggle form government themselves, or to come to some sort of agreement, Mr Green said Labor would stay in power for the short term.

"If the Labor Party loses its majority and is still the largest party, it would be perfectly entitled to stay in office until the parliament sat, in caretaker mode," he said.

But if parliament sits and an agreement still isn't reached, there may be a vote to dissolve parliament.

In short, it means South Australians would go back to the polls and try again.

As to who might make a deal, Green says SA Best is more likely to take Liberal seats than Labor.

And while Mr Marshall, the Liberal leader, has ruled out doing a deal with SA Best, Labor has a long track record of successfully dealing with crossbenchers to form government.

In 2002 Mike Rann became premier with the support of independent Peter Lewis, while at the last election, Mr Weatherill managed to win with the help of independent Geoff Brock.