Less than seven weeks out from election day, the Herald-compiled poll of polls shows support for the National Party still rising, albeit slowly.
The current governing party would be able to rule alone with a comfortable 13-seat majority if the poll of polls calculations were duplicated on election day next month.
A time-weighted rolling average of the country's main polls shows support for National slowly rising to 55 per cent this month, compared with close to 54 per cent last month and 52.5 per cent in July.
Labour's rolling average has slid by nearly five percentage points since July to just over 28 per cent.
The drop in support would see Labour's caucus reduced from 42 MPs to 35, thereby putting several Labour MPs who do not hold an electorate seat in danger of not getting back into Parliament via their list ranking.
Assuming Labour does not lose any electorates it now holds, Steve Chadwick, Stuart Nash and Rick Barker would lose their seats.
In contrast, National would bring in an extra 10 MPs, taking the caucus to 68.
The Herald poll of polls takes in results from the Herald-DigiPoll survey, the One News-Colmar Brunton poll, the 3News-Reid Research survey, the Roy Morgan Research poll and the Fairfax Media-Research International poll.