Labour veteran Annette King has confirmed she will stand again in 2017 but possibly only on the list, a step which would open up her Rongotai electorate for leader Andrew Little.
Mr Little is currently a list MP and if he does not win an electorate he could be the first Prime Minister who is not also an electorate MP.
Although the party vote determines a party's representation in Parliament under MMP, there is still some moral weight in being able to win an electorate and Labour is unlikely to want to take any risks.
Mr Little lives in the Rongotai electorate in Wellington - a safe Labour seat in which Ms King has been the local MP since 1993.
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Asked if Mr Little had asked her to allow him to stand in the seat, Ms King said "that is hypothetical".
"We talk to each other all the time, but I'll make my announcement on what I'm going to do in the future."
She said she would announce her decision "when I'm ready."
Mr Little has stood unsuccessfully in New Plymouth for the past two elections but has ruled out doing so again. He was yet to decide whether to stand in an electorate.
"I'm quite enjoying being a list MP having the flexibility to get around the country doing the job I do."
He said candidate selection for the 2017 campaign had not yet started "so that's a wee way down the track".
Until Mr Little, former National leader Don Brash was the only leader of one of the parties who was not an electorate MP. Mr Little was ranked at 11 on Labour's list in 2014 and only just made it back into Parliament. As leader, he will be ranked 1 in 2017.