Opposition Leader Bill Shorten has heaped praise on Centre Alliance candidate Rebekha Sharkie as he urged voters in Mayo to put the Liberals last in this month's by-election.
Mr Shorten said Labor considered the seat a genuine three-way contest but talked up Ms Sharkie in a none-to-subtle bid to ensure the prized seat doesn't return to the Liberals on July 28.
In his first foray into the Adelaide Hills seat, he said Labor had picked an excellent local candidate in telecommunications consultant and academic Reg Coutts and the party was "chasing every vote we can".
But he described Ms Sharkie, who was forced to resign over the citizenship saga, as "fiercely independent" and criticised Liberal candidate Georgina Downer over what he said was her lack of a local profile and commitment, other than her father's history as the seat's longtime MP.
"Mayo is not someone's family inheritance to be handed on," he told reporters in Mt Barker on Friday.
"The Liberals know that Rebekha Sharkie is a real threat to them so what they're trying to do is smear her and say she's more one way than the other.
"She's her own person. Rebekha Sharkie always puts her case forcefully in parliament.
"She deals with both the prime minister and myself without fear or favour. She 's an advocate of talking truth to power."
"I can understand why the Liberals are threatened by her."
Just down the road, Ms Downer criticised Ms Sharkie's voting record in parliament, saying she had supported the opposition more often on divisions in the house.
"We've got Labor endorsing her so people are asking me the question, if my opponent is elected what will she owe Labor, what will she owe the Greens?" she said.
"They're asking questions and they're pretty concerned about it."
Ms Downer stood alongside Deputy Prime Minister Michael McCormack as the coalition announced $1 million in funding for a study to seek to divert heavy vehicles away from the Adelaide Hills and Mayo tourist town of Hahndorf.
Mr McCormack said the funding was the result of Ms Downer's advocacy, linking her success in the by-election to more infrastructure funding for the region.
"She has told me on numerous occasions just how important it is to get these choke points fixed," told AAP.
"Georgina Downer is in there fighting hard for Mayo."
Ms Downer said she had been heartened by the high level of support she had received during the election campaign.
Mr Shorten committed a future Labor government to approving a new Medicare-rebatable MRI licence for a local hospital to allow people to recover the costs of scans without the need to travel to Adelaide.