Labour might do the unthinkable and cut taxes at next year's Budget if its polling continues to slide, Newshub political editor Tova O'Brien says.

The party and its leader Jacinda Ardern suffered a "parallel plummet" in the latest Newshub-Reid Research poll - Labour down 9.2 points and Ardern 10.6.

"It just goes to show how inextricably linked Jacinda Ardern's polling is with that of the Labour Party," O'Brien told The AM Show on Monday morning. "She is the magic weapon of the Labour Party - the Labour Party needs her."

On Sunday night's numbers Labour would still be in a position to form a Government with the support of the Green Party, even if New Zealand First fails to reach the 5 percent threshold, with the backing of 41.6 percent of voters. 

National is up to 43.9 percent, but - assuming David Seymour wins Epsom - ACT's 1.4 percent would bring in only two MPs, not enough to form a majority for the right-wing bloc. 

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Even so, the difference between the left and right has narrowed - National and ACT are only a few seats away from wresting control of Parliament. 

"Previously people were predicting that Jacinda Ardern and Labour were going to romp home in 2020," political academic Bryce Edwards told Newshub on Monday. "I don't think they can rest on their laurels anymore."

O'Brien says Labour might resort to one of its rivals' favourite ploys.

"I would expect to see some tax cuts in [next year's Budget]," she predicted. "I would expect to see some Budget bribes come next year. When you've got $7.5 billion in the kitty, you're going to throw a little bit of that taxpayers' way in an election year, especially now we've got such a fight on our hands, right?" 

Labour has had a rocky few months, having to deal with sexual assault allegations and the KiwiBuild failure. In June the party was sitting pretty on 50.8 percent, with Ardern receiving praise worldwide for her response to the March terror attack in Christchurch. 

That poll came out the same night a TVNZ-Colmar Brunton poll had Labour way back on 42 percent, prompting suggestions one of them must have been an outlier and completely wrong (which is possible from time-to-time, according to the mathematics behind polling).

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O'Brien suggested it wasn't the Newshub-Reid Research poll that was wrong, saying it was "clearly an accurate reflection of what was going on in the country at the time".

"Now we're seeing this massive tumble, almost a parallel plummet between Jacinda Ardern's failings and the Labour Partys failings in this poll."

Dr Edwards said the poll could have a snowball effect.

"It will start to alert people to the loss of confidence that the public's feeling, and that can be self-perpetuating."

Despite lagging 32 points behind Ardern as preferred Prime Minister, Sunday night's poll will be welcomed by Bridges - his own rating is up 2.5 points to 6.7, pulling ahead of his National Party colleague Judith Collins, who's down 1.9 to 5.2 percent. At those low numbers, both movements are outside the margin of error and statistically significant. 

"He is safe on these numbers... and he will be most heartened I think in this poll by the fact Judith Collins has gone down," said O'Brien.

But he still needs to do something different if he's to get National over the line.

"He's had a personal poll rating bump, the National Party has had a personal poll rating bump, but he's still not in power - and there's still that gulf between his popularity and Ardern's."

As for the minor parties, only TOP saw its support shift outside the margin of error - up from 0.1 to 1 percent. ACT's rise from 0.8 to 1.4 percent was just inside the margin.