Weatherill has stayed away from the media since Xenophon announced on Friday that he would be quitting the Senate to run for the state seat of Hartley in the March 2018 state election.

So far, Xenophon has announced candidates for three Liberal-held seats, one Labor, and one independent – Waite – which is historically a blue-ribbon Liberal seat.

With his move threatening to make a Liberal return to the government benches much more complicated, the party’s leaders have settled on exact opposite strategies.

Weatherill, who snared government after the 2014 election by wooing independent Geoff Brock and then bringing former Liberal leader Martin Hamilton-Smith into cabinet, is being cagey.

He sent out minister Ian Hunter on Friday to comment on Xenophon and today released a brief statement. He would not take questions about whether he had spoken with Xenophon since Friday.

“I welcome Nick back to state politics – lots of choice is good for our democracy,” the Premier said.

Marshall and his Liberals, however, have been aggressive – probably because Xenophon’s personal incursion is into the seat of Hartley, held by Liberal Vincent Tarzia, with threats also posed in the Liberal Hills’ seats of Heysen and Kavel.

Xenophon has a foothold in the Hills through his popular federal member for Mayo, Rebekha Sharkie.

Marshall said today that that Xenophon was offering hope to Labor of holding on to power after 16 years in government.

“The reality is that Nick Xenophon is throwing them a lifeline,” he told ABC Radio Adelaide. “He wants to form a Coalition Government with Jay Weatherill and we could end up with 20 years of dysfunctional Government here in South Australia.”

Earlier, Xenophon told the radio station that if he ended up holding the balance of power in state parliament, a number of factors would determine his decision about who to back into government.

“I care what result can be achieved and it depends on so many factors and I know it’s a reasonable question to ask – who would you support,” he said.

“It’s too early to say: it depends on who wins what seats, it depends on the popular vote, it depends on which side can actually deliver in terms of legislation getting through the Upper House in terms of key reforms. I just want South Australia to be governed much better than it has been for many years.”

Xenophon rejected Marshall’s suggestion that South Australia would be plunged into chaos if his SA Best party held the balance of power, arguing it would lead to greater stability.

“I want this to be a contest of ideas and I think what Steven Marshall said was rather silly because what we want is the opposite of chaos.

“We actually want to build the institutions of good governance, build the institutions of accountability that this state has never seen – if we do all the sorts of things that I was referring to earlier, strengthening those public institutions that have a watchdog role, strengthening the role of Parliament, strengthening the committee system by which there seems to be scant regard to so that contentious legislation goes through a public committee process so we can hear from the experts, hear from the public and hear from the key stakeholders so that we actually get a better result without unintended consequences.

“That doesn’t lead to chaos, it actually leads to much better Government.”

He said he would likely run an open ticket – not directing preferences to either party.

Marshall said the Liberals had a fight on their hands, but he had “trust” in voters.

“I think that they don’t want Labor back in power, they don’t want a hopeless Labor-Xenophon combination in power and I think that they will support us at the next election.”