The last opinion poll to be released before the election put the National Party ahead of Labour by 7.5 points.
Four other polls published on Thursday and Friday also put National in the lead, by greater margins.
The Roy Morgan poll published on Friday evening put National on 42% support, down one point from the previous poll, and Labour up 2.5 points to 34.5% - giving National a 7.5% lead.
Support for the Greens was down 1.5 points to 10%.
New Zealand First was on 4.5%, ACT was on 4% support, the Maori Party recorded 2.5%, while United Future was on 1%.
Radio New Zealand's political editor says the Roy Morgan poll has the smallest gap between the two major parties of the five most recent surveys.
He says under that scenario National would have the best chance of forming a Government, but Labour could still do so if the Maori Party supported it.
The telephone poll carried out between 20 October and 2 November surveyed 1,038 voters and has a margin of error of 3.2%.
National lead in recent polls
Two political polls published earlier on Friday 7 November both put the National Party well ahead of Labour.
The Fairfax Neilson poll showed the biggest gap, with National down two points to 49%, but Labour unable to bridge the gap, also down two to 31%.
And the Herald-DigiPoll showed National down 2.5 points to 47.9%, with Labour down slightly to 36.4%.
The Greens were sitting on 8% in the Fairfax Neilsen Poll and 5.8% in the Herald-DigiPoll.
None of the other parties reached the 5% threshold in either poll.
The Fairfax Neilson poll did not state a margin of error or survey sample size.
The Herald-DigiPoll had 981 respondents and a margin of error of plus or minus 3.2%.
National also had commanding leads in two polls published on Thursday 6 November.
The Colmar Brunton-TV One survey has National steady on 47% support and Labour on 35%, while the Green Party had risen one point to 9%.
ACT was on 2.5%, New Zealand First 2.4%, and the Maori Party 1.3%.
The survey of 1,000 people has a margin of error of plus or minus 3.1%.
In the TV3 poll, National was on 46%, while Labour, on 33.1% recorded its lowest result in that poll in more than three years.
The Greens are on 9%, New Zealand First was on 3.4%, ACT has risen to 2.8% and the Maori Party is on 2.7%.
The poll of 1,000 voters has a margin of error of plus or minus 3.2%.