MPs will vote on Wednesday on whether to send the question of voluntary euthanasia to the public for a final say or dump the issue altogether.
The End of Life Choice Bill - which would allow terminally ill adults to request a medically-assisted death - is up for its third and final reading in Parliament.
If it passes, the question will go to a public referendum alongside the 2020 general election.
The Bill was sponsored by ACT leader David Seymour. He told to Kim Hill he thinks it will pass but he won't be sure until after the vote.
"I'm quietly confident that MPs will line up on the side of overwhelming public opinion that this Bill should pass.
"However, there's still another 12 hours or so to go and we'll be working for every single vote right up to the final bell."
There will be protests against the bill on the lawn of Parliament while MPs vote though. Mr Seymour said that's they're right but New Zealand has been having a debate on euthanasia for years.
"The arguments that have been made are not new. We've had two years of this now. In fact, really New Zealand said 20 years since the Michael Laws Bill back in 1995.
"So, you know, we've had the arguments, I don't think anyone will ever be able to say that Parliament didn't properly scrutinize this Bill. It's been nearly two years since the parliamentary process started.
"Over that time, you know, we've kicked around every conceivable argument for and against the Bill. At this point, it appears that majority is still coming out on side of it."
