The Labour-led left bloc would win government on the latest numbers from the Radio NZ-Reid Research poll, with the Greens the biggest rises.
The Chloe Swarbick and Marama Davidson co-led party has jumped almost five points to 14.8 per cent, a surge consistent with other pollsters.
A month out from polling day, Chris Luxon's centre-right party has charted just 25.9 per cent support.
Down 3.2 per cent in a month and 6.6 per cent in a year, it is the party's worst result in any NZ-based poll this term and in this survey for six years.
"It is a dismal result. There is just no other way to put this," Radio NZ political editor Jo Moir said.
Labour leads on 30.8 per cent, with National's coalition partners NZ First on 10.6 and ACT on nine per cent.
The Maori Party is on two per cent, with upstart force Opportunity on track to enter parliament for the first time on 5.5 per cent.
Labour leader Chris Hipkins leads Mr Luxon as preferred prime minister 22 per cent to 17 ahead of the first leaders debate of the campaign on Tuesday night.
Concerningly for National, the poll also recorded worsening results on two key metrics: Mr Luxon's personal favourability and how many Kiwis see the country on the right or wrong direction.
The prime minister has a net favourability of -24, with more than half - 53 per cent - viewing him as performing poorly, with with the same number describing NZ as on the wrong track.
National has flirted with dumping Mr Luxon has leaders throughout the term, given his polling struggles.
At the latest crunch partyroom meeting in August, its MPs opted against changing leaders, with Mr Luxon sacking defence minister Chris Penk for plotting a coup.
Ms Moir said the results spelled trouble for National, which has held office six times since 1949 and has never failed to win a second term.
"There's not a lot of time to turn the ship around at this point ... with a leader that is tracking backwards and in the negatives," she said.
National campaign chair Simeon Brown told Radio NZ the poll showed "the election is going to be very close, and that there's a lot of work to do".
On the numbers, the left bloc edges leads the right bloc for parliamentary seats, with Opportunity would play the kingmaker role in post-election coalition negotiations.
Its leader Qiulae Wong says she is open to negotiating with either side of politics, but Mr Luxon has ruled out working with them, describing them as radical and left-wing.
Without an electorate seat, the party needs to clear five per cent of the vote to enter parliament, making its performance at the November ballot critical.
18°C