Jacinda Ardern has confirmed to Newshub that she is considering running for the Mt Albert seat.
While it is yet to be finalised, the seat will be vacated by MP David Shearer who is heading to the United Nations.
"If that is finalised I would think about standing," she said. "I am definitely thinking about it."
Ms Ardern stood at the last two elections in the Auckland Central seat against Nikki Kaye.
She said it'd be hard to leave that behind although noted three major suburbs from Auckland Central had moved into the Mt Albert electorate in the last round of boundary changes.
"It's a real dilemma and a difficult decision," she said. "It's a big consideration."
Ms Ardern says she'll make the call soon after Mr Shearer's UN post is finalised.
"You wouldn't want to leave things hanging too long."
And she says the fact that the seat is steeped in history with it being former Prime Minister Helen Clark's won't come into the decision at all.
Earlier on Thursday morning, she declined to answer questions about her potential candidacy.
Mt Albert is a safe Labour seat - Ms Clark held it for 22 years. It has never been won by National since it was established in 1947.
It'll be the second by-election in the electorate in a decade - the Labour seat was up for grabs in 2009 when Ms Clark quit following her loss to John Key in 2008.
Ms Ardern has been in Parliament since 2008 as a list MP. She first stood in the Waikato electorate, then threw her hat in for the high profile Auckland Central seat in 2011 - where she stayed in 2014.
The contest for Auckland Central has been hard fought between her and Nikki Kaye - who has this week returned to Parliament and announced she will contest the seat next year after a shock breast cancer diagnosis.
Ms Ardern has failed to unseat Kaye in both elections - however came within 1000 votes each time.