InDaily revealed last month McLachlan was planning a tilt at the seat vacated by Australian Conservatives founder Cory Bernardi, who was elected on the Liberal ticket in 2016.

He’s standing against Right-backed lawyer Morry Bailes, with fellow conservative and former party treasurer Michael Van Dissel also throwing his hat in the ring.

McLachlan is now considered a soft favourite for the nomination, with anticipated support from the moderate camp as well as a bloc of Right-wingers.

But Bailes supporters are rallying support for their candidate, promoting the contest as a chance to get two capable MPs for the price of one.

“Why wouldn’t the Liberal Party members want both?” said one insider.

“On the one hand, you could have both of them working in the interests of the SA Liberal Party – on the other, you could have only one of them… if you preselect Morry [for the senate], you get Morry and Macca [McLachlan, in the Legislative Council], but if you preselect Macca, you just get Macca.”

Nominations for the party’s 2022 Legislative Council ticket are also open, and will be decided in the days after the senate vote is concluded.

But McLachlan has now confirmed he does not expect to remain in state parliament if his federal tilt fails, and will likely bow out when his current term expires at the next state election.

“At present, I’m focusing on seeking preselection for the senate,” he told InDaily.

“Should I prove unsuccessful then I would serve out my term in the Legislative Council but, having sought the senate and been unsuccessful, it’s unlikely that I would put my hand up for a further term in the Legislative Council.”

A factional stoush is brewing over the Upper House ticket, with the Right boasting a majority on the Liberal’s state council from last year’s AGM.