Coalition negotiations between National, ACT and New Zealand First to form the next government are continuing, five-and-a-half weeks since the general election on October 14, with talks now down to ministerial allocations between the parties.
With the parties' boards yet to sign off, agreements could be announced as early as Thursday and senior National MPs are returning to Wellington today after talks in Auckland over the past few days.
While the top job is National leader Christopher Luxon's, others are circling for the deputy role, and the idea of multiple deputies has been touted.
But University of Otago law professor Andrew Geddis told RNZ's Morning Report today that arrangement would need to be carefully managed to avoid a situation where there was confusion about who the second-most senior member of government was in the event the Prime Minister was unexpectedly unable to act.
Luxon on Tuesday downplayed the office of Deputy Prime Minister as "largely a ceremonial role".
"There's a lot of talk about it - but it's a ceremonial role to fill in for me when I'm incapacitated, away, or not in the House," he said.
However, Geddis said it was "a formal way of saying: this is the next person in line if the Prime Minister, for some reason, can't do something".
Should ACT leader David Seymour and New Zealand First leader Winston Peters share the role - as has been floated - they could potentially play "rock, paper, scissors" to work out which of them would be acting Prime Minister on each of those occasions, Geddes explained.
"The problem would arise if you had an unexpected thing happen so that the Prime Minister couldn't act - at that point you have to work out which of these two deputy prime ministers is the next-most senior, and therefore they would take over."
So while it was possible to appoint two Deputy PMs, "one of them would have to be the 'more senior' Deputy Prime Minister, so that if an unexpected thing happened, they would be the one that would be legally under statute able to take action on the Prime Minister's part".
Geddis said Seymour and Peters would be trying to convince Luxon which of them that should be.
"David Seymour says, 'Well, I'm bigger, I got more votes, it should be me'; Winston will be: 'Well I've done this before, I'm a safe pair of hands'.
"Chris Luxon then has to make a call on which of those he believes - or alternatively try to get rid of the conflict altogether and go with (National deputy leader) Nicola Willis and keep it all in-house."
Seymour said on Tuesday he thought there was a "clear case" for him to have the role of Deputy Prime Minister.
"I think there's a very clear agenda that the ACT Party is the second-largest party in the government and therefore if there's a second role in the government that should go to the second party."
Peters has served as Deputy Prime Minister twice, from 1996 to 1998 (with National) and 2017 to 2020 (with Labour).
This afternoon National deputy leader Nicola Willis, expected to become Finance Minister, said she wasn't in the running and would be happy with either Seymour or Peters.
Traditionally, New Zealand's Prime Minister has had just one deputy. But that is not always the case overseas, with Fiji having three.
Voices at the Cabinet table
Both ACT and NZ First would be demanding a full coalition that allowed them to be in Cabinet at all times, Geddis believed.
"The difference between a full coalition and [an] enhanced agreement - confidence and supply ... to an extent, it's a more of a sort of formalistic thing.
"The important question is, who is going to have ministers? Will they be in Cabinet or not and how will the parties amongst themselves work out what happens when they disagree?"
Geddis said without seats at the Cabinet table, ACT and NZ First would not be able to be part of every decision.
Previous government arrangements under MMP had seen 'agree to disagree' provisions worked through, he said, but it would be up to the parties involved in the next government to navigate those issues for themselves.
"There is a Cabinet manual, there's things that already exist - it's more how it all works in practice between the parties; how confident will they be about doing it, how often will they use it, those sort of questions."