Prime Minister Bill English thinks voters will be bemused by Jacinda Ardern replacing Andrew Little as Labour leader just two months out from an election.
"I'm sure she's a competent politician," he told reporters.
"The real problem for her is the Labour Party and its lack of progress over nine years in opposition - in the end, that's what put the pressure on Andrew Little."
Mr English says it doesn't make any difference to National.
"Under MMP every election is tight, and on current polling we don't have enough levels of support to form the kind of government we think New Zealand needs," he said.
"We have a lot of hard work to do whether it's Andrew Little or Jacinda Ardern."
Other reactions included:
* Politics is hard. Of course Andrew's done a great job for us and we admire the fact that he's made this decision to step aside - Carmel Sepuloni, Labour MP
* To resign as party leader less than two months before an election requires enormous courage. I disagree with Andrew on many things, but he has more honesty and integrity than others on the left. These qualities were on display today - David Seymour, Act Party leader
* Andrew Little spent the last three years standing up for all New Zealanders, working to close the gap between rich and poor. I thank him for that - Metiria Turei, Green Party co-leader
* [Andrew Little] is a person of great integrity and character. It's been a privilege working with you in your time as NZ Labour leader. Warmest congratulations to Jacinda Ardern and [Kelvin Davis]. An outstanding leadership team for NZ Labour - James Shaw, Green Party co-leader
* Holyoake replaced Holland and Moore replaced Palmer as PMs this close to election and both lost. No opposition leader has taken over this close - Peter Dunne, United Future leader
* Andrew Little has fought the good fight, but at the end of the day he was a victim of the transience of the polls - Winston Peters, New Zealand First leader