The Greens have dropped any plans to run a candidate in the Ohariu seat in a move aimed at giving Labour's Greg O'Connor a better chance of winning the marginal seat - despite Green misgivings about his past views.
Green co-leader James Shaw said the decision was taken in the interests of changing the Government, which was the party's priority.
"We have been very clear with our supporters and the public about that since we signed the Memorandum of Understanding with Labour last year," he said.
"Not standing in Ohariu increases the chances that we will be in a position to change the Government in September – it's as simple as that."
His selection pits him against United Future leader Peter Dunne, who currently supports the National Government and has held the seat since 1984.
Prime Minister Bill English would not confirm National would give its voters a "steer" to back Dunne as had in the past saying "we'll deal with that issue later in the year". National had always run a candidate there and would expected to do so again.
However he went on to say: "We'll be focusing primarily on party vote, whatever deals Labour and the Greens are doing are their problem .... we're focused on the party vote in that electorate. National gets a big party vote iand we want to keep that going."
Labour leader Andrew Little said the Green move would be very helpful to O'Connor but he said the Greens had not consulted with Labour before making the decision, though they had told Labour before making it public.
The two parties had talked about possible accommodations last year.
"In the end we agreed that we trust each other enough that we will make our own decisions on standing electorate candidates."
He said there was no "deal" in Ohariu.
"They made a decision not to stand a candidate in Ohariu. They made a decision to stand a candidate in Mt Albert - go figure."
Shaw said the call was made "after many discussions" in the party, which would still campaign strongly for the party vote in Ohariu.
It had no bearing or influence on any other electorates.
But in a statement confirming the decision Shaw made no comment about O'Connor himself.
Green co-leader Metiria Turei has said in the past she does not agree with many of his stances.
O'Connor, a former Police Association boss, was selected on Sunday after being shoulder-tapped by leader Andrew Little.
Since announcing he planned to stand O'Connor has softened his position on arming the police, which he advanced strongly as union boss, noting he had been advocating in line with the views of 70 per cent of his union's membership.
He now says he believes further arming of the police can be avoided.
"I think if effective action can be taken to reduce the number of firearms that criminals in New Zealand have, then it may well be possible to keep New Zealand police not generally armed. But that has to be done," he said his selection.
O'Connor has also taken a slightly softer line on drugs - another area where there could be friction with the Greens - saying after studying overseas approaches he believes there are "better ways to deal with cannabis than just relying on the criminal justice system".
If Dunne is defeated in the seat, which he held with a majority of 710 in 2014 but which has a strong National Party vote, his party is unlikely to make it back into Parliament. It is consistently polling well below the 5 per cent MMP threshold.
The 2014 Green candidate Tane Woodley won 2764 votes compared to 13,569 for Dunne and 12,859 for Labour's Virginia Andersen. National's Brett Hudson won 6120 votes, with many National supporters swinging in behind Dunne.
National won 50.4 per cent of the party vote in Ohariu against 23.5 per cent for Labour, 15.07 per cent for the Greens and just 0.73 per cent for Dunne's United Future.