A bombshell might drop in the South Australian election campaign today when the Independent Commissioner Against Corruption (ICAC) releases a report investigating potential misconduct and maladministration involving the now-closed Oakden aged care facility.

It shut last year after the state's chief psychiatrist found elderly dementia patients were abused and neglected by their carers over a decade.

What is the investigation about?

Commissioner Bruce Lander's report looks at the roles of ministers and public servants involved with Oakden.

The inquiry was launched last May, in the wake of the chief psychiatrist's report.

Mr Lander promised to focus on what information was known by "all people in authority, from local management to executive leadership and ministers" and if they were "aware of the conditions and sub-optimal care being delivered at the facility".

"If information was available that was not acted on in a timely and appropriate manner that might constitute serious or systemic maladministration as defined in the ICAC Act," Mr Lander said.

Why release it close to an election?

Mr Lander had planned for his inquiry to take about six months, but last October he told a parliamentary committee there had been delays obtaining documents and huge volumes of relevant information, pushing out his deadline.

Just recently he said he had been further delayed by three people's attempts to have names suppressed in his report.

At that point, he promised to deliver the report by the end of February.

Who knows what is in the report?

The state's highly restrictive ICAC legislation meant the inquiry was held in secret, even though Mr Lander has advocated for hearings of such alleged maladministration and misconduct to be public, a call repeatedly rebuffed by the SA Government.

Oakden was shut in 2017 after the last residents were moved elsewhere in the state care system. ( ABC News: Matt Coleman )

It also denied the Commissioner access to cabinet documents, even though such a pathway was used by Mr Lander to form his opinion in a previous maladministration investigation — into a government sale of land at suburban Gillman.

Anyone named adversely in his latest report is likely to have seen a draft copy by now, and would have been given the right to respond before the final report's publication at 9:30am today.

What is the likely political impact?

The ICAC report is likely to dominate the election campaign for days, whatever its findings, sucking vital oxygen from Labor's campaign for re-election.

Ahead of the report's release, former mental health minister Leesa Vlahos stood down as lead candidate on the ALP's Legislative Council ticket, but stated she anticipated no adverse findings.

Other key players have also stepped out of the spotlight — a former health and mental health minister Jack Snelling is quitting Parliament after his current term, and Northern Adelaide Health Network chief executive Jackie Hanson has accepted a job in Queensland.

Publicly, Premier Jay Weatherill is welcoming the report's release, just 17 days before voters go to the polling booths.

"We welcome the fact that there will be a public release of the Oakden report and we're looking forward to seeing its findings," he said.

SA Opposition Leader Steven Marshall is eager to remind voters of the Government's efforts to ensure the ICAC proceedings were behind closed doors.

"Labor have done everything they can to keep their scandalous inaction to protect older citizens living with mental health problems from the public gaze," he said.

Oakden nursing home closed after a decade of concerns about injuries and deaths at the facilities. ( Supplied )

SA Best leader Nick Xenophon is unlikely to let the matter rest as he campaigns to win a seat and significant influence in the next parliament.

"This will dominate the election debate at least for this week and, in fact, it should dominate the election campaign until voting day," he said.

"A litmus test for a good society is how we treat our most vulnerable — and those people were treated appallingly."

On Tuesday, a continuing inquest into Oakden care resident Graham Rollbusch's death heard from a nursing administrator about conditions for dementia patients at the nursing home.