A stoush between the Liberals and Nationals could be on the cards over who fills a vacancy initially caused by former minister Fiona Nash's citizenship dramas.
The ex-Nationals deputy leader was disqualified from the Senate in October after it was discovered she held dual UK citizenship by descent, in breach of the constitution.
She was due to be replaced, after a recount, by the next person on the NSW coalition Senate ticket for the 2016 election, Liberal candidate Hollie Hughes.
However, the court declined to declare Ms Hughes duly elected, because she was also in breach of the constitution for holding a job as a part-time member of the Administrative Appeals Tribunal.
The Australian Electoral Commission confirmed on Tuesday it would conduct another special count in Sydney on Wednesday, using voter preference data from the 2016 election.
"Once the special count is completed, the Australian Electoral Officer for NSW, will return the result to the High Court of Australia for its consideration," the AEC said in a statement.
The special count is expected to give the seat to the next Liberal candidate on the ticket, former major general Jim Molan.
However, the High Court's reasons for not declaring Ms Hughes duly elected, which have yet to be published, will determine how the seat is filled.
Solicitor-General Stephen Donaghue told the court on Monday he was acting on the "assumption" that Ms Hughes was "not capable of being chosen" under section 44 of the constitution.
However, Dr Donaghue added if the court's final reasons in the Hughes case found she was "capable of being chosen but not capable of sitting" - that is, was properly elected but was disqualified when she took up the AAT job - it would instead be a casual vacancy which by convention is filled by the party vacating the seat.
The Nationals have been casting around for ways to get Ms Nash back into the Senate, including seeking advice from barrister Bret Walker SC.
"It's a Nats spot and needs to be filled by a Nat. I would expect that a casual vacancy would mean Fiona Nash can return to the Senate," one Nationals MP told AAP on Tuesday.
However, senior Liberals insist the vacancy would be one solely for the Liberal Party to fill, based on section 15 of the constitution.
That section says: "Where a vacancy has at any time occurred in the place of a senator and, at the time when he was so chosen, he was publicly recognised by a particular political party as being an endorsed candidate of that party ... a person chosen or appointed under this section in consequence of that vacancy ... shall be a member of that party."
