The Overhang Machine
NZ election, 7 November 2026

Parliament has 120 seats. Unless it doesn't.

The overhang rule has become a campaign weapon. Break the chamber yourself and see exactly what it does.

Open the simulator How it works
September 2026 poll average with projected electorate wins, looping as more National voters split their party vote

Overhang in five moves

Made-up parties, real rules. Scroll and watch the chamber.

Seats120
Needed to govern61
Overhang0

Your party vote cuts the pie.

Every party that gets 5% of the party vote, or wins an electorate, gets a share of 120 seats that matches its party vote. Blue and Red get 40% each, so 48 seats each. Green's 20% earns 24.

Your electorate vote picks who fills the seats.

Blue wins 40 electorates, so 40 of its 48 seats go to local MPs (solid) and 8 come off its list (faded). Red wins the other 31. Nobody's total changes. The electorate vote decides who, not how many.

Win more electorates than your share, and you keep them.

Now Blue wins 52 electorates, but its party vote only covers 48. A local winner can't be sent home, and no other party loses a seat. So the House grows. The four orange-ringed chairs are the overhang.

The finish line moves half as fast.

A majority is half the House plus one. At 120 seats that's 61. At 124 it's 63. Each extra chair adds a whole seat to one side but only half a seat to the line it has to cross.

This is the detail most coverage gets wrong.

Now the play.

Blue's supporters keep ticking Blue in their electorates but give their party vote to Gold, an ally. Blue still keeps its 52 local seats. Gold collects a full proportional share on top.

That's the move being urged on both sides in 2026: Te Pāti Māori is asking for it on the left; Don Brash and Nick Mowbray have floated it on the right. Try the real numbers below.

Run it on 2026 polls

Run it on 2026's numbers

Start from the polls, pick a split-vote play, drag the slider. Seats are worked out with the same Sainte-Laguë formula the Electoral Commission uses.

Centre-leftCentre-right
Seats in the House120
Needed to govern61
Overhang seats0
Inert party votes0

The tipping point

Bloc seats as the switch grows. The dashed line is the majority, which rises as the House grows.

1. Start from

2. Pick a split-vote play

0%

Nobody switches.

3. Tweak any party

PartyParty vote %ElectoratesSeatsListBloc

Faded seats are list MPs. Orange rings are overhang. Party votes are the share before any switch. Tap a bloc to move a party. Remaining electorates are assumed won by parties not in overhang, which doesn't change any total.

The Overhang Machine: full explainer and sources

Six things people get wrong

Most of the confusion in the coverage comes down to these.

False

"Overhang takes seats off other parties."

Every other party keeps its full proportional share. Nobody is bumped. The House just gets bigger, which is exactly why it can change who governs.

False

"Each extra seat raises the bar by one."

A majority is half the House plus one, rounded down. Two extra seats move the bar by one. That half-seat gap is the whole engine of the strategy.

False

"Splitting your vote like this is illegal."

Splitting your two ticks is normal and lawful. Voters in Epsom have done it for two decades. The rules allow it, which is why people want the rules changed.

False

"This has never happened."

Overhang has happened five times: 2005, 2008, 2011, 2014 and 2023. It has just never decided who governs.

Mostly true

"A party vote for a party in overhang does nothing."

While a party is in overhang, more party votes for it add no seats. But polls can be wrong. If it ends up out of overhang, those votes count again.

It depends

"Switching is risk-free."

A vote moved to a party near 5% is lost if that party misses the threshold and wins no electorate. And a party you lend to may pick a different partner.

It's happened before. Quietly.

Size of Parliament after each election with an overhang. Orange is the extra chairs.

Those overhangs came from small parties with strong local support (the Māori Party, United Future, Te Pāti Māori). 2023's 122 became 123 after National won the delayed Port Waikato vote. What's new in 2026 is the largest party being in overhang, and people organising around it.

Who's saying what

On the record, from both sides and from the people explaining it. Follow the links for context.

"If National wins more electorate seats than its party-vote entitlement, it keeps those seats."
Nick Mowbray, Zuru co-founder · The Spinoff
"There's one plan, two votes; our plan has to be to focus on the candidate votes."
Debbie Ngarewa-Packer, Te Pāti Māori co-leader · RNZ
"Parties follow incentives. If there's an incentive there to do something in a particular way that's beneficial to you, it's something that's going to happen."
Graeme Edgeler, constitutional lawyer · RNZ
"I think voters would punish that kind of game-playing. We've got no intention of doing that."
Chris Bishop, National · The Spinoff
"The right would be unstoppable."
Don Brash, former National leader · The Spinoff
"An absolute rort."
Chris Hipkins, Labour leader · The Post
"The electorates are the meal. The party votes are leftovers, and leftovers can feed an ally."
Oliver Hartwich, NZ Initiative · Unravelling MMP
"Here they are perverting the whole democratic system."
Winston Peters, NZ First, on Te Pāti Māori's plan · RNZ
"It would be profoundly undemocratic."
David Farrar, pollster · The Spinoff

Can it be fixed?

Not before 7 November. Electoral law won't change mid-campaign. After that, there are three options on the table.

Recommended in 2012 and 2023

Abolish overhang seats

Keep the House at 120. The overhanging party keeps its electorate seats and other parties lose list seats to make room.

The Electoral Commission recommended this in 2012 and the Independent Electoral Review in 2023. Neither was adopted. The catch: it caps the House, but gaming still pays because the cost lands on everyone else.

Germany, 2013 to 2023

Compensate everyone else

Every other party gets balancing seats until the result is proportional again. Splitting stops paying. The cost is size: the Bundestag swelled to 736.

Germany, since 2023

Party vote decides, full stop

An electorate winner only takes the seat if the party vote covers it. Overhang disappears, but winning your electorate no longer guarantees a seat, which would hit the Māori electorates hardest.

Embed it. Cite it.

Free for newsrooms, teachers and anyone explaining the election. No tracking in the embed.


      
    

    

      
How the numbers work

      
    
        
  • Seats are allocated with the Sainte-Laguë method under sections 191 to 193 of the Electoral Act 1993: 5% or one electorate to qualify, electorate winners kept, overhang added on top.
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  • Tested against the official 2023 result (48, 34, 15, 11, 8, 6 = 122 seats) and the NZ Initiative's published scenarios (123 seats at baseline; 132 seats at a 25% switch; tipping point 11%). It reproduces all of them exactly.
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  • 2026 has 71 electorates (64 general, 7 Māori) and 49 list seats.
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  • Poll figures: the four most recent published polls (1News-Verian, The Post-Freshwater, Anacta, Taxpayers' Union-Curia, all September 2026), averaged with equal weight, via Wikipedia's poll table.
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  • Electorate wins are a projection, not a poll: the NZ Initiative's uniform-swing figures (National 37, Labour 26, Te Pāti Māori 5, Greens 2, ACT 1). Change them in the table.
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  • Blocs follow the NZ Initiative's grouping. Opportunity hasn't committed to either side. Tap its bloc to move it.
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  • This is a mechanism demonstration, not a forecast, and it doesn't recommend how anyone should vote.
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