LESS than 12 months after a by-election, Mayo incumbent Rebekha Sharkie, Centre Alliance, and Liberal Georgina Downer are again on the husting, for a marginal, yet key, seat.
Formed in 1984, Mayo was solely held by the Liberals until 2016, when then-Nick Xenophon Team candidate Ms Sharkie won the seat.
But Flinders University adjunct professor of politics Haydon Manning said the electorate redistribution, with Adelaide Hills communities Mount Pleasant and Springton lost to Barker and metropolitan fringe suburbs Aldinga and Sellicks Beach incorporated, could work against the Liberals.
He said those areas were "firmly Labor", with a sitting Labor state member.
Dr Manning said Ms Sharkie had gained the traditionally Liberal seat in 2016, partly through "luck", against an "embattled" Jamie Briggs, and with the support of Nick Xenophon.
She gained 55 per cent of the votes in a two-candidate preferred result against Mr Briggs, before extending that lead to 57.5pc against Ms Downer when standing for by-election in July last year, after she was forced to resign during the citizenship saga.
Dr Manning said Ms Sharkie had some advantages as the sitting member, even without the support of Mr Xenophon this time.
"As incumbents often do, Ms Sharkie was able to go to every event and accept every invitation and made her name known, and that ends up rewarding them when they run again," he said.
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He said Ms Sharkie's stance against live sheep exports might cost her farming votes, but those were from people who would likely have voted Liberal anyway, while it might also gain her some votes and preferences from Greens or Labor voters.
Dr Manning said it was possible the Liberals were not expecting a victory against Ms Sharkie but were looking to see if Ms Downer made "credible inroads" with a view to a possible Senate seat.
"She might have to prove the Downer name isn't a hindrance," he said.
Ms Downer's great grandfather was a premier of SA while her father and grandfather both sat in federal parliament.
Dr Manning said, nationally, the 2016 election showed a preference for minor parties and independent candidates, with only 70pc of votes to the major parties.
"With so many minor parties running, it's possible the vote of the majors will continue to decline," Dr Manning said.
"If this trend continues, it's fair to say we are seeing a shakeup and the major parties will continue to diminish and we will see more independents in the House of Representatives."
But he said this trend had been seen before.
He said in 1998, only about 72pc of national votes went to the two major parties but this downward trajectory had not continued at the time.
Candidates for Mayo
Georgina Downer grew up in the Adelaide Hills before working interstate and overseas in her role as a solicitor and consultant, a diplomat with the Australian Embassy in Tokyo and a director of Asialink.
Anne Bourne is a community activist with a background working in community and health services before setting up a private practice as a psychologist in 2011.
ANIMAL JUSTICE PARTY
Helen Dowland has a background in scientific research with the University of Adelaide, and worked for SA Police.
UNITED AUSTRALIA PARTY
Michael Cane is a salesperson.
Saskia Gerhardy has degrees in biodiversity and conservation. She has worked as an environmental educator, coordinator of the Willunga Trees for Life and is the inaugural Young Landcare Ambassador.
Rebekha Sharkie is the Centre Alliance spokesperson for agriculture and rural affairs, education, family and community services, housing, ageing, Indigenous affairs, arts, sport, women and youth. Previously she worked as a paralegal, researcher and policy adviser, with a national advocacy role in the youth sector.