New Zealand First has confirmed it won't stand a candidate in the upcoming Mt Roskill by-election - something John Key says will likely make the contest easier for Labour.
Nominations for the by-election closed today at midday, with seven confirmed candidates.
NZ First joins the Green Party and Act in not running a candidate.
He cut the cord with his electorate, despite having promised to serve them for the full three-year term.
"It probably makes it a little easier for Labour, that's probably why [Winston Peters] did it," Key said this afternoon.
"The more people that stand, the greater the probability that you can get an upset, and that just becomes reduced when New Zealand First is not there, and the Greens are not there and others.
"But...I can't say I was reeling back in my chair when [NZ First] put out a press release."
Key said National's polling indicated that, despite there being a lot of National voters in the electorate, it "was obviously going to be a challenge".
"But we are onward and upward. It is a big task, but not an impossible one."
NZ First leader Winston Peters has campaigned heavily in the regions since winning the Northland by-election in March last year, and over the weekend made a speech attacking "big city" politicians for focusing too much on Auckland.
Mt Roskill includes the suburbs of Lynfield, Wesley, Hillsborough and parts of Three Kings and Sandringham, and less than half of all residents were born in New Zealand.
"Despite a serious number of potential candidates coming forward we will be focusing our resources on the election that matters - the 2017 General Election," Peters said today.
"The Mt Roskill by-election was brought about by the electorate MP deciding to pursue a new job.
"He cut the cord with his electorate, despite having promised to serve them for the full three-year term, and triggered the by-election. The MP's pursuit of personal glory will cost the taxpayer well over a million dollars."
National is gearing up to challenge Labour's candidate Michael Wood for the seat that Goff has held since its creation in 1999.
Goff triggered the December 3 by-election when he resigned from Parliament following his election as Auckland Mayor.
National's candidate is Mt Roskill-based list MP Parmjeet Parmar.
The Green Party last month announced it would not stand a candidate in the by-election, with co-leader Metiria Turei saying it would be closely contested and the Greens didn't want to "play any role in National winning the seat".
That deal is the first in an electorate under the agreement between Labour and the Greens to campaign together more closely and work to increase the centre-left vote.
It could prove critical. In 2014 Goff won with an 8000-vote majority over Parmar but National got 14,275 party votes - about 2000 more than Labour.
Roshan Nauhria, leader of the newly formed People's Party, will also run, primarily on a law and order platform and targeting the roughly 40 per cent of residents who are Asian.
The businessman was one of the founders of the party that launched this year, with the aim of attracting votes from the Indian and other Asian communities.
Act leader David Seymour has confirmed that he would not stand a candidate, so as to give National the best chance of winning.
The other candidates include Richard Goode, who is standing for the Not A Party, which advocates for a peaceful transition to a "free, peaceful and prosperous society based on voluntary cooperation".
In a press release, Goode said he wanted to "keep the seat vacant".
"Let's make Mt Roskill a politician-free zone, with the rest of New Zealand's electoral map to follow suit at next year's general election."
The other candidates are Andrew Leitch for the Democrats for Social Credit, independent Tua Schuster, and Brandon Stronge from the Cannabis Party.
In an announcement linked to the by-election, Labour leader Andrew Little last month released part of Labour's transport policy for Auckland - $680m to help pay for the first stage of a light-rail system from Wynyard Quarter to Mt Roskill.
Little, joined by Wood, set out Labour's plan for the Government to pay half of the $1.36b cost for light rail and Auckland Council the other half.