Most people who have ever used cannabis want it legalised, a new poll has found.
The same poll - commissioned by medicinal cannabis company Helius Therapeutics and conducted by Horizon Research - found the race is neck-and-neck, with 49.5 percent for and 49.5 percent against.
"For nearly two years we've tracked public opinion, and this is an incredible result given early voting starts in just over four weeks," said Helius chief executive Paul Manning, referring to the upcoming referendum.
While non-binding, the present Government is expected to legalise recreational use of cannabis if it's reelected and the vote passes. National has said it might shelve the Cannabis Legalisation and Control Bill if the select committee advises against passing it.
The tight result in the latest poll suggests whether it passes could come down to voter turnout, rather than what the majority actually want, said Manning.
"It's increasingly clear that it will come down to voter registration and election turnout, particularly if younger adults lift their intention to vote."
While 18- to 44-year-olds back legalisation 63 percent, other demographic groups are all opposed - especially 65- to 74-year-olds.
National voters are the most opposed, followed by ACT voters. Green supporters are most in favour, followed by Labour and NZ First.
Slightly more people opposed to legalisation said they were 100 percent certain to actually cast a ballot, suggesting the 'no' vote could have a slight advantage at this stage, despite the tied result.
"This could be the closest vote since 1919, when alcohol prohibition was defeated by just 10,362 votes," said Manning.
"As this survey shows, cannabis is already widely accessible, and so next month's decision is fundamentally about who we want to control it: Government or the gangs."
Most Kiwis try cannabis at some point in their lives. Of those surveyed, 70 percent of those who had were in favour of legalisation. The demographic most likely to have tried cannabis is those aged 35-64.
Over the past year-and-a-half of polling on the subject by Horizon, the number of people saying they're unsure has dropped from 16 percent to 1 percent. Most who were once unsure but have since made up their minds have opted to vote against legalisation.
The polling was done August 20-25, and weighted for age, gender, highest education, personal income, employment status and party vote. The maximum margin of error is 2.7 percent.