Liberal Senator Zed Seselja will face off against a moderate challenger in his first preselection battle since ousting sitting senator Gary Humphries.
It is understood former naval officer and current Department of Defence employee Sam Fairall-Lee will be nominating for the Canberra Liberals' preselection.
Kacey Lam, also a moderate, is understood to be nominating for the number two position on the Senate ballot paper.
Mr Seselja, a leading conservative within the party, has held the Senate seat since beating moderate Mr Humphries in a bitter preselection battle in 2013.
He was preselected unopposed before the 2016 federal election.
The moderate forces within the Liberal Party have been attempting to whittle away conservative control of the ACT Liberal branch.
Mr Fairall-Lee, described by some as a defence and national expert, has been a member of the party's moderate wing for nearly 10 years.
He is a former naval officer and current reservist and works as a senior civilian officer with the Department of Defence.
He declined to comment when contacted by The Canberra Times.
Ms Lam ran for the seat of Ginninderra at the October ACT election.
Any challengers to Mr Seselja have until November 12 to put their hand up, with a list of valid nominations announced three days later.
The party's management committee sent out a notice to members last month, saying preselection would take place on November 23.
The move to preselect a Senate candidate so far out from the next federal election was criticised by Mr Seselja's opponents, including former Liberal president Gary Kent.
Mr Kent said it was a cynical move to avoid competition for Mr Seselja.
The next federal election could be as early as August 2021, however, Prime Minister Scott Morrison last month indicated he would not seek to head to the polls before 2022.
It comes amid ongoing tensions between conservative and moderate factions within the party, which came to a head after the recent election loss.
Moderate Elizabeth Lee was installed as leader after the defeat, replacing the conservative Alistair Coe.
After the election, Mr Humphries said the party was destined to spend decades longer in opposition unless conservative forces in the party relinquished power.
He claimed even with a moderate leader, conservative members would still be able to control it unless it underwent significant reform.
