New Zealand has voted under MMP 10 times. Through all 10 campaigns, the parties honoured an informal rule found in no statute. You do not game the voting system. Everyone knew the system had a soft spot. Nobody built a strategy around it because each party assumed voters would punish the first one that tried.
The soft spot is called overhang. The party vote decides each party’s share of Parliament’s 120 seats; the electorate vote only decides who fills them. But a party that wins more electorates than its share keeps them all, and parliament simply grows to make room. Win seats the cheap way, through electorates alone, and your allies can harvest the party votes you no longer need.
On Sunday, the old rule died. At its campaign launch in Gisborne, Te Pāti Māori publicly and deliberately asked supporters for exactly this split: candidate votes for the party, party votes for another party of the left, turning the Māori electorates into bonus seats.
On current polling, the play is worth three or four additional seats for the left bloc. That is a distortion of the system, albeit a modest one. The greater problem is what it invites: a response in kind from the other side of the political spectrum. And this year, the response would not be modest.
Because this year, of all years, the other side has a far bigger opportunity of the same kind waiting in plain view. On current polling, close to 900,000 people will give National their party vote, and none of those votes will yield an additional seat.
National is on track to win about 37 electorates, one more than its share of the vote would give it. Its seats are already settled by the electorates alone. Whatever its supporters do with the party vote, National ends up with the same 37 seats.
A National voter who understands this needs no instruction from anyone. Her party vote is dead where it is but alive anywhere else on the centre-right. Moving it to ACT buys an additional seat and takes nothing from anyone else. She is not cheating. She has simply read the rules, as Te Pāti Māori’s voters are now explicitly invited to do.
The numbers are startling. If one National voter in nine reasons this way, the governing coalition wins a majority that current polling denies it. If one in four does, the coalition wins 69 seats in a parliament of 132, even though the opposition parties, between them, won more votes.
This is the outcome MMP was meant to make impossible. New Zealand adopted it after 1978 and 1981, when the party with more votes lost the election. Tactical voting on this scale would bring the wrong winner back, this time inside the proportional system itself. And none of it would break any law.
That is the problem: the law itself invites it.
All of this lands under a promise already made. Christopher Luxon will put MMP to a referendum if he is re-elected. Public support for the system is real but soft. In the most recent poll, 53 per cent would keep it, 29 per cent would change it, and nearly one in five cannot say.
An election that unravelled from two sides, by a left party gaming the Māori seats and right voters gaming the party vote, would write the case for MMP’s abolition better than any campaign could. It does not have to end that way. Germany, which invented this electoral system, lived through the identical story and cured it in 2023 by abolishing the overhang. New Zealand runs a more exposed version of the same machine and has left the flaw untouched since the Electoral Commission recommended repairing it in 2012.
Nothing can change the rules before 7 November. But everyone should understand precisely what the rules allow, because one party is already asking voters to use them, and arithmetic will tempt the rest.
After the election, whoever governs should repair the machine before asking New Zealanders whether to keep it. An electoral system that punishes sincere voting and rewards clever voting will not stay legitimate for long.
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This article was originally published by the New Zealand Centre for Political Research.
