Senator McKenzie has said she won’t run for the Mildura-based seat, but speculation continues she would be interested in the lower house seat of Indi, currently held by independent Cathy McGowan.
Mr Broad announced his resignation from Mallee following his admission of inappropriate conduct.
Nominations for Mallee pre-selection opened on January 4 and the contest will be held on January 19 at Birchip.
Social worker Anne Webster is the first person to publicly declare her nomination for the Nationals in Mallee.
Ms Webster is a director of a not-for-profit organisation which supports young mothers.
Ms Webster, who recently concluded studies for a PhD, was also a pre-selection candidate for Mallee in 2013.
Meanwhile, a senior Liberal MP is calling for quotas to ensure more women are selected as candidates for federal parliament.
Assistant Minister for Regional Development and Federal Member for Farrer Sussan Ley is urging the NSW division of the Liberal party to pick a ‘‘sensible number’’ such as 40 per cent to improve the party’s reputation for female representation.
‘‘Of course it needs to be implemented as soon as possible,’’ Ms Ley told The Australian newspaper on Friday.
‘‘I’ll certainly be encouraging my NSW division, where honestly there are some really good women who are pushing this barrow.
‘‘You have to pick a sensible number and date but then we’re heading in the right direction, we’re heading away from what is a bit of a cliff face.’’
Ms Ley’s colleague Jason Falinski also believes the party should do more to ensure future candidates are from more diverse backgrounds.
‘‘Clearly men and women are equal,’’ the NSW MP said.
‘‘I don’t think the community expects us to fix it overnight but they do expect to see us addressing the issue.’’
The Liberal Party currently has 21 female candidates and 102 male candidates for the House of Representatives ahead of the federal election, which is due by May.
However, candidates have not been confirmed for 10 electorates.
Women hold 12 of the Coalition’s 74 seats in the lower house, with the number dwindling after Julia Banks quit the party to sit as an independent.
Gilmore MP Ann Sudmalis also announced in September she won’t recontest the election, pointing the finger at bad behaviour in the NSW division, as Jane Prentice lost pre-selection for her Brisbane seat.