The main race might be over, but there are several compelling battles that remain ongoing in the South Australian election, with Legislative Council members Kelly Vincent and Robert Brokenshire likely to exit Parliament.

Two Lower House seats — Adelaide and Mawson — are too close to call, but the Liberals look set to retain Heysen in the Adelaide Hills despite a strong challenge by SA Best.

But the make-up of the Legislative Council will make negotiating a tough time for the new Liberal Government.

The most likely result in the Upper House is four seats to Labor, four to the Liberals (including Jing Lee), two SA Best candidates (Frank Pangallo and Connie Bonaros) and a Green (Tammy Franks).

That would mean neither Mr Brokenshire (Australian Conservatives) nor Ms Vincent (Dignity Party) retain their seats.

"That would be two SA Best gains at the expense of Dignity," ABC election analyst Antony Green said.

"I don't think the Conservatives are going to get any preferences under the new electoral system."

Bearing in mind that only half of the Upper House was up for election, that result would take the overall composition of the chamber to eight Labor, eight Liberals, two Greens, two SA Best, an independent (John Darley) and a Conservative (Dennis Hood).

Dignity Party MP Kelly Vincent entered Parliament in 2010. ( ABC News: Isabel Dayman )

But what will that mean for the incoming government?

While the Liberals might have had their fingers crossed for an Australian Conservatives victory (Mr Brokenshire was once a Liberal minister), securing four seats is about as good a return as they could have expected.

Jing Lee, who was fourth on the Liberals' ticket and launched an aggressive campaign for re-election, looks likely to have retained her seat.

But the overall composition of the Upper House will mean the Liberals will need the votes of at least four crossbenchers to make new laws.

"What this result most likely means is that the Upper House will be about equally split into thirds — Liberal, Labor and crossbench," Greens MLC Mark Parnell said in analysis he posted on Facebook.

Robert Brokenshire was elected in the 1993 Liberal landslide. ( ABC News: Nick Harmsen )

"It means that for contentious legislation, the new Liberal Government will need four out of six (or maybe seven) crossbench members."

"Contentious legislation" would likely include deregulation of shopping hours.

Last week, Premier-elect Steven Marshall declared that he would have a "mandate to make sure that we can deregulate shop trading hours" should his party win the election. But the policy is not supported by the Greens.

"With about two thirds of the seats in the Upper House counted, it looks like the Greens will hold that 10th or 11th seat which will mean I join Mark Parnell in that crossbench," Greens MLC Tammy Franks said.

"We will absolutely fight the deregulation of shop trading hours. We will stand up for penalty rates for workers, for workers' rights."

Greens candidate Robert Simms and Tammy Franks, who has retained her Upper House seat. ( ABC News: Matthew Doran )

Ms Franks said her party remained the "third force" in SA politics, despite the emergence of SA Best.

"We will be there to protect the environment, put essential services back in public hands," she said.

"We will stand against a nuclear waste dump being put in our state, as much against the Liberals as when Jay Weatherill had that idea as well."

Deregulated shopping hours are also strongly opposed by SA Best. That party's vanquished leader Nick Xenophon was today upbeat about his party's results, despite the collapse it suffered on polling day.

Xenophon rules out taking Upper House spot

At one point, SA Best was predicted to secure 32 per cent of the primary vote but looks destined for less than half of that number.

"It's not how you fall, it's how you get up," Mr Xenophon said today.

"If you look at the vote, it's still a respectable vote of over 200,000 South Australians, but we were spread too thin.

"I'm sorry that I couldn't get across the line in Hartley and I'm also very sorry for my colleagues who put up a good fight in many seats where we came close, but not close enough."

Jing Lee looks likely to have secured her Upper House seat. ( ABC News: Tom Fedorowytsch )

Mr Xenophon said, with counting still ongoing, there would not be "any formal concessions of defeat".

He acknowledged he could have chosen another seat where election might have been an easier task, but has ruled out occupying either of his successful candidates' seats under a casual vacancy.

"I'm not interested, either state or federal, so can we just rule that out so there isn't any speculation," he said.

However, he did leave the door open to the prospect of another run for office in four years.

Sanderson and Bignell battling for survival

Meanwhile, the battles for the Lower House seats of Adelaide and Mawson remain ongoing.

In Adelaide, Liberal incumbent Rachel Sanderson is marginally ahead of Labor challenger Jo Chapley, who has so far secured a swing of almost three per cent.

"That's going to be tough because we've still got a lot of pre-polls and postal [votes] to go," outgoing Premier Jay Weatherill said.

Liberal Rachel Sanderson was elected to Parliament in 2010. ( ABC: Spence Denny )

And Labor's Leon Bignell is ahead in Mawson, despite a boundary redistribution widely tipped to favour Liberal candidate Andy Gilfillan.

Despite a very tight race, the seat of Newland in Adelaide's north-east is also likely to fall to Liberal challenger Richard Harvey.

Pre-poll votes are strongly tipped to favour the Liberals, and incumbent Labor MP Tom Kenyon last night conceded defeat in a Facebook post.

"I would like to take this opportunity to congratulate Richard on an exemplary campaign," Mr Kenyon said.

"He has worked hard for a long time and deserves his win. I wish him well for the next four years."

Bernardi concedes Conservatives have underperformed

Australian Conservatives leader Cory Bernardi was disappointed with the result for his party, admitting it was unlikely to win an Upper House seat.

"We haven't met our expectations, I'll level with you," Senator Bernardi told ABC Radio Adelaide.

"We're about four or five thousand votes short of where I thought we would be and we'd have to get a very good preference flow.

"I'm very saddened if Robert Brokenshire can't continue because he's been a true champion for South Australia in the Legislative Council."

Robert Brokenshire and Cory Bernardi at the Conservatives' campaign launch. ( ABC News: Tom Fedorowytsch )

But the senator was more pleased by his party's performance in the Lower House, securing a primary vote of about 3 per cent.

He said that result had prevented SA Best candidates from securing seats in the House of Assembly.

"Our Lower House work did make a difference in some seats," he said.

"I like Nick Xenophon personally but I don't think his style of politics and negotiation has ended up in good outcomes."