National Party leader Simon Bridges says his MP Agnes Loheni let him know she'd be contesting the candidacy for Botany, adding it's a "free world".
Former Air New Zealand chief executive Chris Luxon had already confirmed he'll be putting his hat in the ring for what is regarded as a safe National seat.
The party's looking for a new candidate after sitting MP Jami-Lee Ross, now an independent, left the party in explosive fashion last year.
Mr Bridges was asked whether Ms Loheni, a list MP, sought his advice before putting her name forward.
"She certainly let us know and it's a free world, National's a party that likes competition to get the best talent."
The selection process was gruelling, he said.
"You have many people....really put you through your paces, who want to understand every aspect of your life and your character and what you'll bring to Parliament."
He expected other MPs and board members to stay out of the selection process so it's done "fairly and by the rules".
'The best man or woman will win."
There was no pushback from party members disgruntled by the fact a high profile outside candidate had entered the race, said Mr Bridges.
"We want a contest and we want the best person to come forward, and I know that the delegates of Botany, National Party members, many of them, will choose that person."
He declined to say who he would like to see win the seat.