Zed Seselja has resigned as leader of the Canberra Liberals to challenge ACT senator Gary Humphries for his upper house seat.
The Liberals’ eight MLAs will gather in one week to elect a new leader for the territory’s branch.
Mr Seselja officially announced his move at a press conference at the Assembly early on Monday afternoon, after serving just three months as member for Brindabella, the electorate where he moved before October’s territory election.
The announcement will leave Mr Seselja in a head-to-head race for pre-selection with Senator Humphries who has held the seat since 2002.
“I’m taking this step because I think I’m the best person to represent the ACT and the ACT Liberal Party in the Federal Parliament,” Mr Seselja said.
But Mr Seselja repeatedly refused to “bag” the man who was once his political ally.
“I have a lot of respect for Gary Humphries, I respect the contribution that he continues to make, I don’t take anything for granted," he said.
Asked if had already secured the numbers to roll Senator Humphries, Mr Seselja said that he did not know.
“I certainly believe that I have a strong level of support within the party, as to the exact numbers, I don’t know and that will become apparent in the coming days,” he said.
Mr Seselja said that, if successful at preselection, he would continue his duties as an MLA, probably up until the official federal campaign began on August 12.
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Mr Seselja said it had been "a great honour" to lead the Canberra Liberals, but it was time to move on.
“In the end, you’ve got to make decisions, and renewal is important in political parties," he said.
Mr Seselja said he did not know who he would support to take his position as Canberra Liberals leader, and said the decision was up to party members.
"I believe that I leave the parliamentary Liberal Party in a better place than when I found it," he said.
"Whoever takes over that leadership will be well-placed to take government in 2016."
Senator Humphries told Fairfax earlier on Monday, "As the first ACT Liberal ever to serve on a federal front bench I'm very proud of my record and I intend to ensure that the members of the Liberal Party in the ACT are appraised of my work and my achievements in this coming preselection I look forward to offering good reasons why I should be preselected once again for the Senate seat."
The preselection ballot is expected to be held on February 23.
ACT Chief Minister Katy Gallagher has predicted Mr Seselja will be the next Liberal Senator for the ACT.
Speaking before Mr Seselja confirmed he would challenge Senator Humphries for preselection, Ms Gallagher said she didn’t believe Mr Seselja would be challenging unless he had the numbers.
“I doubt very much that Mr Seselja would be nominating for something he is not going to win … within the Liberal Party,” Ms Gallagher said.
Mr Seselja is expected to use his popularity in the recent ACT elections to convince party members to support him. He led the ACT Liberals to their best result in an ACT election, however, Labor managed to retain power by making a deal with the sole cross bencher, Greens MLA Shane Rattenbury, to make him a minister.
Senator Humphries - who is also a former ACT Liberals opposition leader, as well as a former ACT chief minister - was elected to the Senate in December 2002 to fill the casual Senate vacancy caused by the resignation of Margaret Reid.
He is shadow parliamentary secretary to the shadow attorney-general and shadow parliamentary secretary for defence materiel.
Mr Seselja would need to resign his seat as an MLA to contest the federal election, however, he would only need to do this after winning pre-selection and once nominations are open. This would not be until the weeks before the election.
Under the ACT's Hare-Clark electoral system, there would be a countback of Mr Seselja's votes among Brindabella candidates who choose to be involved. Initial indications are Val Jeffery - the prominent former local bushfire brigade captain from Tharwa - would be the front runner to win that seat.
Earlier this morning, former Labor ACT deputy chief minister David Lamont told ABC radio that, politically, Mr Seselja had no choice but to stand down as Liberal leader.
“One would assume that the Liberal Party would internally look at trying to bring somebody in as leader as soon as possible, if in fact he was going to take a tilt at Gary’s position,” he said.
“I just don’t think politically that they could have a leader who was telling the people of Canberra that he was a leader in the local Assembly, but ‘Oh I am going to the big house on the hill’. I think that politically, that is one hump too far.”
Mr Lamont said there were a number of options in the ACT Liberals to replace Mr Seselja, including his deputy, Brendan Smyth who was previously party leader, and Molonglo MLA Jeremy Hanson.
“I think you have got a couple of candidates who would obviously stand out, obviously Jeremy. I think Brendan would, just because he would have to, and I think the more interesting thing is you have some new blood in the Liberal Party,” he said.
“[Alistair] Coe from Belconnen has really shown his mettle in the last few years and matured tremendously as a local representative. Inside their party I think they have got probably an obvious succession group, both as leader and very probably as deputy leader.”
There has been speculation Mr Seselja could turn his focus to federal politics since shortly after the October ACT election, particularly after the resignations of three powerbrokers.
Stephen Doyle stepped down from his position as Opposition Leader Zed Seselja's chief of staff last month and was reportedly considering a move into the federal arena. Party president Tio Faulkner quit as Mr Seselja's director of electorate services, and Victoria Taylor has resigned as the party's general secretary.
with staff reporters