"Let's party. We won." With those words Kris Faafoi launched himself into Parliament as the first New Zealand MP from Tokelau after winning the Mana byelection tonight, beating National candidate Hekia Parata by 46.4 per cent of the counted vote to 41.6 per cent.

The result was a 14 per cent swing to the National candidate since the 2008 general election.

Mr Faafoi, accompanied by wife Gina Faafoi-Rogers and 23-month-old son George, took the stage to rapturous applause, flanked by Labour leader Phil Goff and former MP for Mana Winnie Laban.

An emotional Mr Faafoi thanked his supporters and paid special tribute to an uncle who was on his deathbed, but had told him he couldn't wait to get better so he could start waving placards on the campaign trail.

Afterwards he said it had been a hard-fought victory, but he was elated and looking forward to getting stuck into his parliamentary work and being a "strong voice" for Mana.

"This puts you through the wringer, this process. You're away from your family. If you're the favourite, you get targeted ... We stayed classy. We held our own and I'm happy with that."

Less than 50 per cent of registered voters turned out to give Mr Faafoi a 1080 majority.

There are 1353 special votes still to come, but it is extremely unlikely to change the result.

Mr Faafoi won 10,397 votes; Ms Parata won 9317 votes.

Green Party candidate Jan Logie won 1493 (6.6 per cent); independent candidate Matt McCarten, who many feared would split the left vote, won 816 votes.

Act candidate Colin du Plessis won 132 votes; Julian Crawford, from the Aotearoa Legalise Cannabis Party, won 107 votes; Sean Fitzpatrick, from the Libertarians, won 43 votes; and Kelly Buchanan, from the Alliance Party, won 37 votes.

Both main parties claimed the result as a victory. The majority was slashed to 6155, though there were 12,372 fewer voters.

In 2008 labour's Winnie Laban won 53 per cent of the vote, compared with Ms Parata's 35 per cent.

The total vote count was 22,387 out of 48,000 registered voters, which Labour said accounted for some of the result.

When asked about the swing, Mr Faafoi said: "We won tonight. Fullstop."

Mr Goff said he wasn't disappointed with the slim majority.

"It was a win. It was a very clear win. It's not in doubt.

"There are no second prizes in politics."

Mr Faafoi said he was happy to be the first MP from Tokelau.

"It makes me very proud. My parents sacrificed a lot, came here with nothing and now their son is a member of parliament. This is a big way that I can repay the sacrifice that my parents made."

Prime Minister John Key said it was a great night for the National Party.

At the start of the campaign Mr Goff had said the byelection would be a referendum on the Government's policies "and he was right."

The result was bad news for Mr Goff's leadership, Mr Key said.

"It is a victory," Ms Parata said thanking her supporters.

"It has shown the people of Mana that there are other options."

The Green Party's Jan Logie caught 6.6 per cent of the vote, coming in third. Independent Matt McCarten, who many feared would split the left vote, won only 3.6 per cent.

The main contenders had been relentlessly pounding the streets over the past weeks. Mr Faafoi claims he has lost 10kg with the amount of doorknocking he has done.

It has been a clean contest, though media have provided the candidates with plenty of opportunities to insult the other challengers.

One of the main focuses has been the lack of local candidates - only Green Party candidate Jan Logie and Act's Colin du Plessis live locally.

The big three of Mr Faafoi, Ms Parata and Mr McCarten can't even vote in the byelection because they don't live there.

Mr Faafoi came under fire early on for implying in his brochure that he grew up in the electorate, when he in fact grew up in Christchurch.

"I had a great start because my family settled in Mana," the brochure said.

Right-wing blogs also had fun at his expense after he claimed he remembered when the first McDonalds restaurant, which would have been when he was 1 year old.

He later said he had misspoke, but that didn't stop bloggers posting digitally altered photos showing a smiling Kris Faafoi sitting among former Labour heavyweights David Lange and Mike Moore in the 1980s, or standing next to a young Elvis Presley and watching the King of Rock'n'Roll shake hands with then-US President Richard Nixon.

While Mr Faafoi was accused of being an outsider coasting to the candidacy courtesy of a shiny endorsement from his leader Phil Goff, Ms Parata found support in some unlikely places because of her presence in the electorate over the past three years.

Mr Faafoi mainly pushed the line that most people were struggling to make ends meet under National's policies, while Ms Parata pushed the exact opposite view - that the Government's policies were making life easier.

This may have given voters an easy choice - vote on how you think the Government has made an impact.

Mr Faafoi managed to sidestep a potential sore when one of his supporters called a fellow Pacific Islander a "dumb-ass coconut" for supporting National.

Ms Parata, too, ran a strong campaign. The main stumble she had was when she literally tripped over one morning, but none of the TV crews at the event managed to record it, saving her the indignity of it being replayed over and over.

She faced a group of protesters at the official launch of her campaign, a small group of locals who were against the expressway through the district from MacKays Crossing to the north of Otaki.

She also had to absorb a barrage of criticism because some public meetings about the expressway - where locals expected to be told which properties, if any, might be affected - were postponed until after the byelection.

Coincidence? asked Labour and the Greens.

But Ms Parata stayed afloat, and it must have been a relief for National supporters to see a good campaign after the train-wreck in Mt Albert last year, when Melissa Lee lost heavily to Labour's David Shearer.

Independent MP Matt McCarten put some fire into the campaign, though many feared that the union leader would further split the left vote; no one on the right - with all due respect to Colin du Plessis - was really going to take a bite out of Ms Parata's vote.

Mr McCarten pushed three policies, and tried to paint the others as void of their own ideas and just harmless extensions of their own parties.

He, too, had hurdles. In Porirua this week a Labour supporter heckled him relentlessly for gifting victory to Ms Parata because of the fractured left vote.

This may have pushed him to galvanise his own supporters to heckle Prime Minister John Key and Ms Parata the following day as they walked through a mall, an obvious publicity stunt that duly made all media reports that evening and the following morning.

Byelection results:
Kris Faafoi (Labour) 10,397 votes
Hekia Parata (National) 9317
Jan Logie (Green Party) 1493
Matt McCarten (independent) 816

Colin du Plessis (Act) 132
Julian Crawford (ALCP) 107
Sean Fitzpatrick (Libertarians) 43
Kelly Buchanan (Alliance) 37

Turnout: 22387 votes, 47 per cent turnout (using 2009 figure of 48,000 registered voters)