Labour and the Greens are chalking up the Mt Albert by-election as a successful test of how the parties will work together but stand against each other in electorates in the general election.
Julie Anne Genter and Jacinda Ardern. Photo: Green Party / RNZ
Jacinda Ardern won the safe Labour seat with more than 75 percent of the vote, and a majority of 8500 over her nearest rival, the Green Party's Julie Anne Genter.
Ms Ardern said she never thought about just how big her margin of victory would be.
"Regardless of what the result was, we took nothing for granted this by-election, we'll take nothing for granted going in to the general election.
"For me, I'll go back and review the numbers, but we'll work just as hard in the general election campaign. The result won't change a thing for us."
Labour leader Andrew Little said the win gave his party confidence it was doing the right things ahead of September's general election.
"I think if you look at the combination of the Mt Roskill by-election, the local government election and now this election, we got our vote out because of the hard work Jacinda and her team did," he said.
"I feel very confident about the quality of our organisation, the issues that we've picked and what we're going to be campaigning on."
Jacinda Ardern and Andrew Little after she won the Mt Albert by-election. Photo: RNZ / Sarah Robson
The by-election was also a test run for the memorandum of understanding between Labour and the Greens, and how they might work together, while still competing against each other.
Mr Little said the two parties would be standing against each other in a lot of electorate seats in September.
"We are also competing to maximise our respective party votes, but Jacinda [Ardern] has proven that a party with whom we have a good relationship, with whom we have some common ground, we can compete with as well in an election, but do so in a respectful way that doesn't destroy the relationship."
Ms Genter, who got 11 percent of the vote in the by-election, said voters wanted to see more of political parties working together.
"I think the by-election has been a huge success in showing how two parties can work together constructively and positively, and still be standing for slightly different policies," she said.
"I think that many New Zealanders want to see their politicians acting like friendly adults and being co-operative."
Well back in third place was the candidate for Gareth Morgan's Opportunities Party, Geoff Simmons, who got 600 votes - just under 5 percent.
Mr Simmons said they were testing the electoral waters and they achieved what they set out to do.
"We managed to get 5 percent within that time and lifted people's understanding of what the Opportunities Party is all about.
"But there is a pretty big lot of apathy to overcome, hopefully if we can tap into those people and motivate them to vote for something different, then we'll have a chance in September."
Ms Ardern's victory means Labour will get a new list MP, with Raymond Huo set to return to Parliament.
Until now, Ms Ardern has been a list MP, having twice unsuccessfully contested the Auckland Central seat.
Special votes are still to be counted and the final result will be announced on 8 March.