The latest Roy Morgan poll shows National up slightly but it may not have captured the full reaction of voters to the fallout and allegations from Nicky Hager's Dirty Politics book.
It puts National support at 48 per cent, up two percentage points from the last Roy Morgan poll in July.
Support for Labour drops 2.5 points to 27.5 per cent and the Green Party loses 0.5 points to 11.5 per cent - a total of 39 per cent for a Labour-Greens coalition.
NZ First rose to its highest level of support since September 2013, up 1.5 points to 6.5 per cent.
The rise in support takes it over the 5 per cent party vote threshold required to enter Parliament under MMP and puts leader Winston Peters in a potential kingmaker role again.
Support for National's coalition partners fell slightly overall with the Maori Party on 1 per cent (down 0.5 per cent) and ACT and United Future both unchanged on 0.5 per cent.
The Internet-Mana Party was unchanged on 2.5 per cent.
Colin Craig's Conservative Party was also unchanged at 1 per cent.
The poll was taken between August 4 and 17. Hager's book was released on the night of August 13, so the poll only captured reactions to it in its last few days.