New Zealand elections are conducted using the MMP voting system - Mixed Member Proportional. Its defining characteristics are a mix of MPs from single-member electorates and those elected from a party list, and a Parliament in which a party's share of the seats roughly mirrors its share of the overall nationwide party vote.

It is a proportional system, which means that the proportion of votes a party gets will largely reflect the number of seats it has in Parliament.

Each voter gets two votes.

The first vote is for the political party the voter chooses. This is called the party vote and largely decides the total number of seats each political party gets in Parliament.

The second vote is to choose the MP the voter wants to represent the electorate they live in. This is called the electorate vote. The candidate who gets the most votes wins. They do not have to get more than half the votes.

Under current MMP rules, a political party that wins at least one electorate seat OR 5% of the party vote gets a share of the seats in Parliament that is about the same as its share of the party vote.

For example, if a party gets 30% of the party vote it will get roughly 36 MPs in Parliament (being 30% of 120 seats). So if that party wins 20 electorate seats it will have 16 List MPs in addition to its 20 Electorate MPs.

Coalitions or agreements between political parties are usually needed before Governments can be formed.

Going into this election, National governs with the Support of United Future and its MP for Ōhāriu, Peter Dunne, Maori Party and their MPs and Co-Leaders Te Ururoa Flavell, MP for Waiakiri and Marama Fox who was elected as a List MP and is the Maori Party Candidate for Ikaroa-Rāwhiti and David Seymour from ACT who is the MP for Epsom. 

This election comes on the back of some major changes in New Zealand politics. Firstly, with the mid-term resignation of John Key and the ascension of Bill English to the top job. In this election, he seeks a mandate in his own right. Secondly, we see the mid-campaign resignation of Opposition Leader Andrew Little and the ascension of his Deputy Jacinda Ardern. Her rise to the leadership with Kelvin Davis as her Deputy Leader has given the Labour campaign a new momentum and energy that Labour has not seen since the election defeat of Helen Clark.

This has seen Labour's poll numbers rise to 32.5% according to Roy Morgan, 37% according to UMR and 33.1% (Reid Research). While UMR traditionally has a Labour bias, all three polls show National falling but Labour making most of its gains from the Green Party who have seen support fall since the resignation of one of its Co-Leaders, Metiria Turei.

At the last election, National achieved its best result under MMP, winning 60 seats and Labour had its worst election ever. The Labour Party’s share of the vote in 2014 (25.1%) is the lowest it has achieved in any MMP election to date; it is also the lowest share for the Labour Party in any election since 1922 when its 23.7% vote share was third-highest behind the Liberal and Conservative parties.

There are 25 MPs who have self-identified as being of Māori descent or 21% of the total Parliament; there are a record eight MPs who identify as being of Pacific Peoples ethnicity, or 7% of the Parliament; there are five MPs who identify as being of Asian ethnicity, 4% of the Parliament.

Our analysis of recent NZ wide polling is that either National or Labour would need the votes of New Zealand First and Winston Peters to govern.

Newshub-Reid Research poll has New Zealand First at 9.2% and third in the party standings. This poll has neither the Greens-Labour Coalition and the National-ACT-United Future Coalition couldn't govern without New Zealand First. 

According to the TVNZ-Colmar Brunton poll the Green Party could be out of Parliament as a result of the Labour new leader's popularity and the fall-out from Metiria Turei's resignation. The Greens have dropped 11 percentage points to 4 percent, according to the TVNZ-Colmar Brunton poll - its worst result in the poll since 2009. In this poll, New Zealand First polls at 10%.

With United Future Leader, Peter Dunne resigning from Parliament as the MP for Ohariu; this leaves National in a dangerous position of not having enough support party MPs without Winston Peters.

It should be noted that in neither poll, National polls over the 45% 'firewall' it needs to be sure of its majority against the Labour-Greens Coalition.

What we are seeing in New Zealand with the rise of Ardern is similar to what we saw in the United Kingdom, the condensing of the vote around the major parties as voters sure up their major party and move away from 'split' voting, which is normally voting differently between the electorate vote and the party vote. 

Therefore, with an election on September 23; people should be watching for the following:

  • How high can the 'Jacinda Effect' take Labour?
  • Can the Greens recover? 
  • Can the National vote get above 45%

We also say to people to watch the debates. John Key was an excellent debator and gained momentum from the debates. Right now the momentum is certainly with Ardern and with Bill English moving to centre his campaign on spending commitments to arrest the momentum back from Labour, the debates will be key.