A poll of the Northland electorate predicts a clear win for National's Grant McCallum, who is 25 points ahead of Labour incumbent Willow-Jean Prime.

NZ First's Shane Jones looked to be coming in third, and only about 11 percent said they were undecided.

The Taxpayers' Union-Curia poll had a sample size of just 400 due to the lower voting population when polling for an electorate compared to the whole country.

It was the same methodology the outfit has used for its other electorate polls, like in Ilam, but means there is a higher margin of error, of +/- 4.9 percent at the 95 percent confidence interval. This - and the fact it is a single poll, rather than a trend - makes it less reliable than the nationwide polling.

Voters were asked which candidate they would vote for if the election had been held the previous day:

• Grant McCallum (National): 43 percent
• Willow-Jean Prime (Labour): 18 percent
• Shane Jones (NZ First): 13 percent
• Reina Penney (Greens): 4 percent
• Matt King (Democracy NZ): 4 percent
• Mark Cameron (ACT): 2 percent
• Undecided: 11 percent

A further 2 percent said they would vote for a Te Pāti Māori candidate although none has been announced, 2 percent would vote for others, and 1 percent refused to answer.

The result suggests a clear defeat for Prime, who won the seat in 2020 on a slim margin of 38.1 percent of the vote compared to the 37.7 percent of King, who was at the time standing for National.

King had held the seat in 2017 with 38.3 percent, defeating Prime (21.6) and Winston Peters (34.8).

The poll was taken on Sunday, 10 September. Results were weighted for demographics.

This story was originally published by RNZ