Angus Taylor will face his first major campaign test as opposition leader when voters go to the polls to choose a replacement for the woman he ousted.
A by-election will be held in the regional NSW seat of Farrer on May 9.
The vote was triggered by Sussan Ley's resignation from parliament on Friday after Mr Taylor rolled her to become opposition leader.
The southern NSW electorate takes in the regional cities of Albury and Griffith, and stretches to the South Australian border, covering 126,500 square kilometres.
A four-way race is expected to choose Ms Ley's replacement, with the Liberals, Nationals, One Nation and Climate 200-backed independent Michelle Milthorpe planning to run.
Ms Milthorpe who second in the 2025 election, narrowing the Liberals' margin to 6.2 per cent in the previously safe seat.
She issued a statement shortly after the by-election date was announced declaring she was "ready to fight".
The Liberals, Nationals and One Nation are expected to announce candidates soon.
Pauline Hanson's anti-immigration party has announced a shortlist of three possible contenders: agribusiness professional David Farley, small business owner Leigh Wolki and farmer Guy Cooper.
Nationals Leader David Littleproud played down his party's prospects of winning the seat but said he hoped he could help the Liberals retain it.
"It'd be very hard for us to poll ahead of any of those, we haven't been there for 25 years," he told the Inside Politics podcast when asked about his prospects against the Liberals, One Nation and Ms Milthorpe.
"I believe our role will be to try and garner some of that One Nation vote back to our side and to the coalition, and then hopefully be able to siphon that off for preferences with the Liberals."
Voters have until April 8 to update their details with the Australian Electoral Commission, with formal candidate nominations closing on April 13.
