A new poll has the National Party falling well below 50 per cent support, and the Labour Party surging 6.5 percentage points to 30 per cent support.
The latest Roy Morgan Poll has National down 5 percentage points to 46 per cent, a 4 percentage points ahead of the Labour-Greens block, which has increased 3.5 percentage points to 42 per cent.
It is the lowest result for National since May.
The Greens dropped 3 percentage points to 12 per cent, while New Zealand First fell 1 percentage point to 5 per cent.
There was little change for National's support parties: the Maori Party on 1.5 per cent (up 0.5 percentage points), and both Act and United Future on 0.5 per cent (no change).
The poll bucks the trend of other recent polls, including the Herald-Digipoll and Colmar Brunton poll, which had National between 52 and 55 per cent, and Labour between 24.9 and 28 per cent.
The Roy Morgan poll period included the resignation of National MP Claudette Hauiti, and Transport Minister Gerry Brownlee's offer of resignation for breaching airport security.
It also included a Labour source criticising Labour leader David Cunliffe's vacation in Queenstown.
The Internet-Mana Party alliance is on 2.5 per cent (up 1 percentage point).