South Australian Opposition Leader Steven Marshall says the state election will go "down to the wire" while Premier Jay Weatherill has declared the Liberals "not ready" for government.
With no clear front-runner, Nick Xenophon is urging voters not to panic if there's no clear result next Saturday, saying "the sky won't fall in".
Mr Marshall spent the weekend campaigning with federal heavy hitters; Prime Minister Malcolm Turnbull on Saturday and Foreign Minister Julie Bishop on Sunday.
He's vowed to campaign "every second of every day" until the close of voting.
"I think this election will go right down to the wire," he told reporters on Sunday.
"People were saying there was going to be a Liberal win at the last election and we ended up with another four years of dysfunctional Labor administration."
Mr Marshall said voters were also "waking up" to the idea that a vote for SA-BEST and Mr Xenophon could simply return the Labor government.
But Mr Xenophon said the election was shaping up as a genuine three-cornered contest in a number of key seats.
"We need to wait for the dust to settle and for everybody to be pretty calm," he said.
"I note that Belgium didn't have a government for about 12 months and seemed to function quite well.
"It might be that we won't know for a week or two, but the sky won't fall in."
Campaigning in the Adelaide Hills seat of Heysen, where support for Mr Xeneophon's candidate is thought to be strong, Ms Bishop urged against a vote for SA-BEST, describing it as a "wasted vote".
With her own family having close connections to the region, she said Heysen residents should support Liberal candidate Josh Teague.
"I've been campaigning in a number of seats and as this one is my old territory we thought it was a good idea to come along and back Josh," she said.
"I think he'll make an outstanding member for this area."
Mr Weatherill took his aim on Sunday at the Liberals, questioning their ability to get "basic sums right" and ask the right questions to formulate policies.
He said that was evident in a policy to cut the construction time for the Adelaide 500 V8 circuit from 25 weeks to 21 weeks.
The premier said the time taken to put up and pull down the temporary grandstands and other infrastructure was already under 20 weeks.
"When have you ever seen a bad opposition make a good government?" he said.
"They're not ready. In four year's time, they might just be ready for opposition."