ACT leader David Seymour says he needs another 21 MPs on side if his voluntary euthanasia Bill is to become law.
The End of Life Choice Bill was drawn from the ballot on Thursday, meaning Parliament will debate whether to allow dying patients to choose when and how to end their own lives, rather than leaving it to fate.
"It says if you have a terminal illness like cancer that doctors say will end your life within six months, or if you have a grievous, irremediable condition - something like Huntington's disease - and you're in a state of decline, then you can be examined by two doctors who have to decide that you're of sound mind, that you understand the decision that you're making," Mr Seymour told The AM Show on Friday.
"If you get through all that then you can be given the means, or have a doctor end your life at a time of your choosing. That's compared to the alternatives people right now - starve themselves to death, commit amateur suicide, or their doctors give them a bit too much morphine."
It'll be a conscience vote, meaning MPs won't vote along party lines.
"We've got 40 onside, we need ," said Mr Seymour.
"There's 27 who have said no. That leaves a very big bunch of MPs in the middle who haven't made up their mind or have never said anything at all, so we can't tell."
Around three-quarters of Kiwis have expressed support for some kind of voluntary euthanasia in recent polling. An unscientific poll of The AM Show visitors on Friday found 84 percent in support.
Mr Seymour's Bill doesn't go as far as previous attempts to legalise euthanasia.
"A previous Bill that Maryan Street had in the ballot would allow someone with say, dementia, to have another person, perhaps a power of attorney or family member, make that decision for them after they'd lost their own ability to decide," said Mr Seymour.
"I didn't put that in my Bill. One of the principles of my Bill is that only the person concerned can make the decision for themselves."
Despite that, conservative lobby group Family First has vowed to "kill" the Bill.
"One of the main reasons that politicians in New Zealand have rejected previous attempts to decriminalise euthanasia is that they realised that the safeguards, while sounding good, would not guarantee the protection required for vulnerable people including the disabled, elderly, depressed or anxious, and those who feel themselves to be a burden or are under financial pressure," says Family First director Bob McCoskrie.
"The international evidence backs up these concerns, and explains why so few countries have made any changes to the law around this issue. We simply need to ensure a palliative care regime in NZ that is fully funded and world class. That's where the politicians' focus should be."
Facts over fear
Mr Seymour is convinced MPs will back his Bill if the debate sticks to "facts rather than the fear-mongering".
"There are people who for various motivations will say things all sorts of things that aren't true about what happens overseas."
Mr Seymour's Bill was drawn from the ballot on the same day one by Green MP Julie Anne Genter that would make it legal to grow marijuana for medical purposes. Coincidentally, both causes were backed strongly by union leader Helen Kelly, who died of cancer in October last year. She openly used medicinal marijuana, and called for assisted dying to be made legal.
Paula Bennett 'undecided'
Deputy Prime Minister Paula Bennett told The AM Show she is still undecided, but wants to make a decision soon "because I don't need thousands of emails in the next few days".
"I just at least want to take the weekend. I just need a few days. I haven't read the Bill myself, and I'm kind of busy."
She says having worked in rest homes and hospitals, she's "sat with people while they've died. I've seen the worst of it. Many people, actually."