Former Labour MP Maryan Street has decided she doesn't want to return to Parliament, even though she's next on the list if her party wins the Mt Albert by-election.
Ms Street was an MP from 2005 but failed to get re-elected in the 2014 election. She remains on the Labour list.
Jacinda Ardern's probable win in the February 25 by-election would pave the way for Ms Street to return as an MP.
However she has revealed she doesn't want the job. Her stepping aside leaves a path for Raymond Huo, also a former MP, to return to Parliament.
Ms Street confirmed the decision in a Facebook post on Monday night.
"I have thought long and hard about this choice and have decided that I can be just as effective on issues dear to me outside Parliament as inside - perhaps even more so.
"Besides which, I have discovered weekends."
Before her departure from Parliament, Ms Street had an End-of-Life Bill which had yet to be drawn from the ballot.
She withdrew it in 2013, fearing it would become a political football the following year.
Despite that, she's remained a campaigner for euthanasia.
"The campaign for a law change to allow End of Life Choice has gained a powerful momentum with the petition in my name to Parliament's Health Select Committee, where submissions are still being heard.
"I am heartened that it has become an issue with wide support throughout the community and across the entire political spectrum. I look forward to advancing that campaign further," she says.
Mr Huo was first elected to Parliament in 2008, becoming Labour's first MP of Chinese descent.
He was re-elected in 2011, but didn't make the cut in the 2014 election.
There was some confusion within Labour about who would be bumped up into Parliament should the party win the by-election.
Leader Andrew Little believed it would be Moana Mackey, however she's since ruled herself out from a return.
A list MP herself, Ms Ardern is expected to win the Mt Albert seat left vacant by former leader David Shearer who left the party for a top United Nations job in South Sudan.
Ms Ardern is up against a slew of candidates including Green MP Julie Anne Genter, Opportunities Party candidate Geoff Simmons, independent candidate Penny Bright and Socialist - People Before Profit's Joe Carolan.
National decided against running a candidate in the seat which has been held by Labour since it was first contested in 1946.
As of February 19, there had been just under 2000 advance votes.