Retiring Labor senator Stephen Conroy is set to be replaced by a former senator and senior Victorian political staffer.
Mehmet Tillem previously filled a casual vacancy in August 2013 when David Feeney resigned from the Senate, but was defeated at the 2013 election.
The first Turkish-born member of the Australian parliament is a close Right faction ally and former chief of staff to Senator Conroy.
Asked whether Mr Tillem was guaranteed the seat, Labor leader Bill Shorten said the party was still going through its processes.
"I'm sure there will be a whole range of very good candidates emerge," he told reporters in Sydney.
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"That process has not been concluded at all."
