The National party will choose a new leader in the next 24 to 48 hours, senior whip Barbara Kuriger says, and former leader Simon Bridges is not ruling out trying for the job again.
The party's senior leadership team was informed of Todd Muller's resignation last night. Its MPs are converging on Wellington for a 7pm meeting this evening and RNZ spoke to some at the airport.
Former National leader Simon Bridges for one was not ruling out putting his hand up to take his old job back.
Bridges, who was rolled as leader by Muller in May, told reporters at Wellington Airport the situation was "really sad".
"I'm thinking about him and his family at this time. You know - I think a lot of people say, but I know - being leader of the opposition is the toughest job in politics.
"It's also a tough time for the National Party and, you know, I suppose at the end of the day when the going gets tough the tough get going and we've got some difficult discussions and choices to make over the next little while".
When asked whether he wanted the job back, and whether he would reinstate Paula Bennett as deputy, Bridges responded "let's see what happens".
He did not respond when asked whether he would rule out putting his name forward for the leadership.
Speaking to RNZ at Auckland Airport, Judith Collins would not say whether she was ruling herself in or out of the running for the top job.
She said she was leaving the decision up to the caucus and she felt "really sorry" for Muller.
"Obviously we'll be leaving all that matter up to our discussions... I'm just going to have those discussions in caucus," Collins said.
"I'm certainly a member of the wonderful National Party team and I'm happy to be so."
At Wellington Airport, acting National leader Nikki Kaye was not ruling out putting her hand up to take over the role permanently, either.
Kaye said the caucus would go through a process to select a new leader.
"What is important at this time is that we have compassion for Todd", she said.
National MP Mark Mitchell was not ruling out putting his hand up to take over as leader of the party either.
Mitchell threw his hat in the ring for the leadership when Bill English stood down in 2018, but Simon Bridges was chosen by the caucus instead.
He would not say if he would put his hand up again.
"I will not be drawn on that at all because I have said I will respect the process and the process is we will come together as a caucus this evening and we'll work out what we're going to do from there."
The party did not want to be in its current position, he said, but he had confidence it could still win September's election.
Coup a mistake, Dowie says
Outgoing National MP Sarah Dowie said the party's leadership coup in May was a mistake and Bridges should have remained as leader.
At Wellington Airport this afternoon, Dowie said the situation was unfortunate and she was sad for Muller.
She would not say who she backed to take over as leader, instead saying "I've got to consider the options".
MPs quiet on leadership options
List MP Simon O'Connor ruled out running for the leadership himself and would not indicate who he would back.
"[Todd Muller's resignation] came out of the blue but I'm looking forward to some very robust discussions today to take the party forward.
"I think you can take one thing for certain that I won't be running for the leadership."
Asked what he thought of Muller's resignation, Paul Goldsmith said: "very disappointed".
Goldsmith said the plan now was to "get back on track" as quickly as possible.
Gerry Brownlee would not speculate on who he would support but said he respected Muller's reasons for stepping down.
"Mr Muller is a very fine New Zealander, a man I've got a great deal of respect for. This is not a very pleasant situation that we find ourselves in," Brownlee said.
"There'll be plenty of time in the future to reflect on all of this."
Nelson MP Nick Smith told reporters at Wellington Airport that today was a "difficult day for the National Party".
"But we will get through these difficult times and we'll get focused on the election campaign as a united team".
Rangitata MP Andrew Falloon would not be drawn on who he was backing to take over as National's leader.
"Look, I'm not sure who is putting their name forward yet, that's a caucus decision to go through later on tonight.
"I've got many opinions, but they'll be expressed in the caucus room later tonight", he said.
MP Louise Upston would not comment on who she would like to see lead National.
"If we make a decision today that's great, if we don't it's really important for the country to know the National Party has their best interests at heart, so we will be selecting a leader that we believe has the attributes and ability to lead our fantastic party for now and in the future," Upston said.