The Auckland Central electorate, held for four consecutive elections by National's Nikki Kaye, looks set to turn red.
A Newshub Nation-Reid Research poll has Labour's Helen White way out in front in the three-way race for the seat, despite her relatively low profile.
White is on 42.3 percent, with National's Emma Mellow on 26.6 percent and the Greens' Chloe Swarbrick on 24.2 percent.
With 20.7 percent of voters still undecided, there's only a slim chance Mellow can pull off an upset and keep the seat for National.
Auckland Central has historically been a Labour seat, only losing it once between 1919 to 2005 (in 1993 to the left-wing Alliance).
All of Kaye's victories arguably came as a result of Greens and Labour supporters splitting the vote - every single win was been by a margin so small that if every Green voter had given their vote to the Labour candidate, Labour would have won the seat - and vice versa.
There's still a chance the vote will be split, with many Labour voters at this stage planning to vote for Swarbrick - 15.7 percent. Only 60 percent of Labour voters said they were definitely going to vote for White.
In June, White told RNZ voters should pick her because she'd "do this job very seriously", dismissing Swarbrick as a "celebrity". Swarbrick later tweeted White was "using the same attacks against me that misogynists do".
"It's a seat with very very strong contenders, and I don't underestimate them," she told Newshub Nation.
"It's something I learnt last time, things can change very very quickly and I'm not taking anything for granted."
Mellow has much stronger loyalty from National supporters, with 77.9 percent planning to give her the tick. She thinks the poll is wrong.
"I've talked to thousands of voters since I was selected. I don't think the results are as they are - our support is much higher and it's solid and it's growing... When this poll was conducted I'd been the candidate for less than a month. Most of that time we were in lockdown so that really hampered our efforts to be campaigning."
Swarbrick has similar loyalty from Green voters, with 77.1 percent on board, but 16.5 percent are planning to give the tick to White.
She thinks the race is "very tight", despite White's polling.
"This is gonna come down to the people of Auckland Central. Auckland Central does not belong to a political party, it belongs to the people of Auckland Central."
Only 43.2 percent of voters are planning to give their candidate Jenny Marcroft their candidate vote.Demoted to 17th on the party's list, it's likely her political career is over for now.
Just over half - 55.2 percent - of ACT voters are going to vote for Mellow and 22.3 percent to candidates from other parties.
As for the party vote, most Auckland Central Labour voters in 2017 - 77.6 percent - are planning once again to give Jacinda Ardern the tick. Only 4.7 percent are going to vote for National instead, and 9.6 percent the Greens.
National voters aren't so loyal, with only 68.6 percent saying they're going to tick blue in 2020 - 15.7 percent are switching to Labour.
The poll had more bad news for the Greens though - barely half of their voters in 2020 plan to vote Green in October. A quarter have switched allegiance to Labour.
White and Labour have ruled out giving Swarbrick the nod to ensure the Greens make it back into Parliament.
"Never. I would not. And it's been made very very clear by Jacinda Ardern that it's not on the cards."
"We're not looking for a deal," added Swarbrick, "and to be quite frank I think what this shows is that people get to make a decision for the type of candidate that they want."
The news is even worse for New Zealand First, with only 22 percent saying they'll back Winston Peters again - half are switching to Labour and 12.4 percent to National.
Overall, Labour had 56.2 percent support, up 18.4 percent on 2017, and National 23.1 percent - down 16.1 percent. The Greens had 12.1 percent, ACT 3.9, NZ First 1.6, the Opportunities Party 1.4, New Conservatives 0.8, Advance 0.6 and the Māori Party 0.3.
The most recent nationwide Newshub-Reid Research poll had Labour able to govern comfortably on more than 60 percent. Subsequent polls by others have had the party between 48 and 53.5 percent. The Greens have hovered around the 5 percent mark, and are in danger of being bundled out of Parliament if Swarbrick fails to win Auckland Central.
For the new poll, Reid Research interviewed 532 people in the Auckland Central electorate via landline, mobile, online and on the street in the first and second weeks of September. The results were weighted to match the electorate's demographics. The margin of error is 4.2 percent.