Three people are on the shortlist to replace the disgraced Southland MP Todd Barclay after a prominent farmer was rejected.
Parliament's youngest MP withdrew as National's candidate for the Clutha-Southland electorate six weeks ago after he confirmed allegations he made secret recordings of his electorate secretary.
The police have since reopened their investigation.
National has named the three candidates as Vanessa van Uden, Hamish Walker and Nick Perham.
Ms van Uden was a business consultant before serving as a popular mayor of Queenstown for six years.
Mr Walker is a property manager who moved to Dunedin in 2014 to be National's candidate for Dunedin South, and was credited with lifting the party's standing in what used to be Labour heartland.
Mr Perham works as an assessment manager at Worksafe New Zealand, and was elected to the Southland District Council last year.
The trio are from a long-list which reportedly had nine names on it, including the recently retired chief executive of the Community Trust of Southland, John Prendergast.
Another person turned down was Allan Baird, the Southland president of Federated Farmers, who agreed to withdraw his nomination after talks with National Party leaders, he confirmed today.
Mr Baird is being prosecuted for a major effluent spill from his dairy farm at Benmore, which polluted the Winton Stream last October.
He was disappointed his name could not go forward because he would have liked the opportunity to contest the seat, he said.
And he thought he would have been one of the stronger candidates were it not for the court case.
The prosecution by the Southland regional council might be resolved next month, and he hoped to avoid a court battle because he had reported the breach himself, Mr Baird said.
The Clutha-Southland electorate including much of rural Southland, South Otago and the Queenstown area, has been safely held by National since it was created in 1996.
The now Prime Minister, Bill English, held the seat until 2014, when he opted to become a list MP.
National's local electorate committee will hold a series of meetings during the next fortnight to decide their candidate for September's election, for a final decision in Winton on 16 August.
Whoever is chosen is odds-on to be the next MP for Clutha-Southland.