Election 2023: Herald’s Poll of Polls show Labour’s re-election chances seem to be evaporating

The likelihood of Labour forming a Government, even with Te Pāti Māori and the Greens’ help, is now lower than the likelihood of a hung Parliament, the Herald’s Poll of Polls reveals.

The Poll of Polls runs a simulation based on polling data from multiple public polls and previous election results to get a feel for what might happen if the election were held this weekend and for what might happen on election night.

Running that simulation multiple times provides a sense of how likely various outcomes might be. The latest simulation takes data from last night’s Newshub-Reid Research poll.

National and Act have a 59.1 per cent probability of being able to form a Government if the election was held this weekend.

Labour, the Greens and Te Pāti Māori have just a 17.9 per cent chance - lower than the likelihood of a hung Parliament - which is 22.9 per cent.

Taking the simulation out to polling day on October 14 changes things slightly.

National and Act are still the most likely governing partners, with a 56.4 per cent chance of getting over the line.

Labour, the Greens and Te Pāti Māori’s chances improve slightly to 29.9 per cent. That puts them ahead of the likelihood of a hung Parliament, which has a 13.6 per cent chance.

The Poll of Polls also looks at voting intentions across the multiple political polls to see what party vote support the different parties are likely to command.

This shows how tight the election is likely to be.

National would be on 34.5 per cent, with Labour close behind on 32.3 per cent.

Act follows on 12 per cent, with the Greens on 9.3 per cent. New Zealand First is on 3.7 per cent, just ahead of Te Pāti Māori, which is on 3.5 per cent.

TOP is on 2.4 per cent.

How the Poll of Polls works

As part of its 2023 election coverage, the Herald is launching its Poll of Polls, which combines polling from different pollsters to predict the party vote for the 2023 election.

The model imagines that in any given week there exists an unobserved voting intention that is partially measured via opinion polls and is accurately measured once every three years by an election.

The model can also make predictions about how voting intentions can evolve between now and election day.

This approach enables us to estimate each polling organisation’s accuracy in previous elections and then use that to inform our predictions.

The Herald has based its model on a New Zealand election forecast developed by statistician and data scientist Peter Ellis. Ellis developed the model in a private capacity prior to taking on his current role as director of Statistics for Development Division at the Pacific Community (SPC).

Ellis also used the model to forecast the Australian election. Similar models have been used to make predictions about the German and Swedish elections. Both Germany and Sweden have proportional representation electoral systems similar to New Zealand’s MMP system.

Our Poll of Polls combines results from a range of pollsters, who are signatories to the New Zealand Political Polling Code, specifically Curia, Kantar Public, Talbot Mills, and Reid Research.

Details of the model, including the source code, are available here. Between now and the election, we will be looking to improve some aspects of the model, in particular the handling of polls which do not provide polling data for some of the smaller parties.

Currently, in order to be included in the model, a party must have polled over 2.5 per cent in at least three polls.

It is assumed that parties currently holding an electorate seat retain them and no other parties win an electorate seat. Future versions will enable readers to modify this assumption.