The poll of voters showed 61 per cent of Kiwis said they voted "yes" in the binding referendum on the End of Life Choice Act, with 29 per cent against and 10 per cent unsure or refused to say.
The Curia Market Research poll was commissioned by the Act Party and was weighted to gender, age and area from the 2017 election and also to party vote for the 2020 election.
It specifically asked: "In the referendum on support for the End of Life Choice Act, did you vote yes or no?"
Exit polling is illegal in New Zealand so the poll was taken between Sunday and Tuesday night.
Age and gender turnout for the 2020 election is not yet known so the final referendum result could differ from the Curia poll. But the outcome is highly unlikely to be different given the huge margin between 'yes' and 'no' votes.
The preliminary results of both the End of Life Choice Act and the cannabis referendums will be released by the Electoral Commission tomorrow at 2pm.
Support for the End of Life Act started strong with a 1 News Colmar Brunton poll in April last year putting it at 71 per cent but the margin slowly narrowed over time to the same poll putting support at 60 per cent the week of the election.
Act leader David Seymour was the bill's architect and said the results of the poll today were "very encouraging".
"It appears the New Zealand people have ratified Parliament's decision and thousands of New Zealanders in years to come, instead of excruciating deaths, will have control, dignity and choice over their own bodies.
"I call on opponents of the legislation to cease from negative campaigning and respect the international evidence that these laws are safe.
"If they don't like the law, the civilised response should be to not choose it for themselves, rather than criticise those who do."
The Herald approached opponents of the Act but they were either unavailable before this story was published or wanted to wait until the preliminary results of the election are released tomorrow.
