Act candidate David Seymour is comfortably ahead in the latest poll in the key seat of Epsom - as long as people vote with the National-Act deal in mind.
A Colmar Brunton poll on Epsom, released on TVNZ's Q + A programme this morning, also showed that the Labour Party is lagging behind the Green Party in the race for the party vote.
The National Party is streaks ahead at 60 per cent support.
The poll showed initially that National's Paul Goldsmith was well ahead on 44 per cent, leading Mr Seymour on 32 per cent.
But asked to keep in mind the National-Act deal in Epsom, in which Mr Key has encouraged National voters to give their electorate tick to Mr Seymour, the Act candidate jumped to the lead at 45 per cent.
Mr Goldsmith's support fell from 44 per cent to 31 per cent. He is only seeking the party vote.
Almost half of those polled - 47 per cent - said they supported the deal. Only 37 per cent opposed the deal.
Conservative candidate Christine Rankin was a distant fifth on 4 per cent, trailing the Green's Julie Anne Genter on 10 per cent, and Labour's Michael Wood on 9 per cent.
In the party vote, the Green Party was on 16 per cent, followed by Labour on 14 per cent.
In an electoral debate on Q + A this morning, Ms Genter said National telling voters to vote for Mr Seymour was "undemocratic".