Zed Seselja has promised an energetic, grassroots campaign for the Senate after ending Gary Humphries's political career.
Mr Seselja won Liberal Party preselection, 114 to 84, to be the lead Senate candidate in a ballot of party members on Saturday that was marked by angry protests.
He urged party preselectors to embrace generational change and recognise his strong campaign in the Legislative Assembly.
''I do think we need to secure that Senate seat and make it a less vulnerable seat than it has been in recent years,'' he said after the meeting. ''We can do better, the Greens really shouldn't be a threat to this Senate seat.''
Mr Seselja did not directly criticise Senator Humphries, who has held an ACT Senate spot for 10 years and served for 14 years previously in the ACT Assembly.
Former ACT Liberal president Gary Kent said Senator Humphries had been ambushed by not allowing all his supporters to vote. Some party members emerged from the meeting with signs saying, ''Shame Zed''.
Senator Humphries congratulated Mr Seselja on his ''decisive win''.
''I'm sad after a very long career in politics to have to bow out but one's time is up sooner or later and obviously today the view of members is that my time is up,'' he said.
''I would have wished there were more members of the party able to take part but I accept that the members have spoken.''
The result looks certain to be challenged at an extraordinary general meeting of the party’s ACT division next month.
Divisional president Tio Faulkner confirmed on Friday that a group of members had collected enough signatures to force a meeting of all members to try to overturn the result and stage the preselection again.
ACT Chief Minister Katy Gallagher called on Mr Seselja to resign from the Legislative Assembly.
''As the now endorsed Liberal candidate for the Senate, Mr Seselja has made a very clear and very public statement that he no longer wants to be an MLA and, in light of that, I don't think it's reasonable or fair for him to continue to draw a wage as an MLA while campaigning to be elected to the Senate,'' she said.