Can we really trust the polls?

A polling expert on how simultaneous polls can tell such different stories, and the choices media make in reporting.

The opinion polls are coming thick and fast in the final days of the 2026 NZ election campaign. But when two emerge at the same time delivering markedly different results, as they did last week, should we be sceptical about the story they tell? 

“The main answer is simply margin of error,” said Murray Campbell, spokesperson for the Research Association of New Zealand, on At Large with Toby Manhire. In that latest example, the gap could be simply that the RNZ/Reid poll had “plumbed the lower level of, say, National’s share of vote, and the Verian poll [for 1News] found the upper reaches of that margin of error”. It was “annoying and a bit unsettling”, he said. “But that's the most logical reason.”

There were some other factors that could affect the results, including the means by which respondents are contacted. Reid uses an online panel while Verian is 50/50 panel and phone. “One could argue that the split methodology of mobile phone via random digit dialling and the online panel gives a broader spectrum of chance for voters to be interviewed,” said Campbell.

There was also the approach to weighting – the means by which pollsters sought to ensure there was a demographic sample that reflected the population at large. Taken together, he said, “it's both a science and an art”. 

What about the risk of self-selection, especially with those panels? “An online panel that's specifically set up for research purposes, like Dynata, has recruited over many years, over many different streams, to get this cross section of New Zealanders, and it's actively managed,” he said. “They have really sophisticated techniques to assess whether people are answering truthfully and engaged with the answer, so it's not just haphazard.” 

They wouldn’t, for example, simply take the first people who responded, but repeat efforts to contact potential respondents, to ensure that busier people were not underrepresented in the sample, he said.

Speaking on RNZ this morning, Labour leader Chris Hipkins said: "the media have lost their minds in their absolute obsession with polling at the moment." But what does Campbell make of the reporting?

“I think the media needs to look at itself in the mirror, to be honest, about the words it uses to describe a two- or three-point shift,” he said, pointing to the likes of “‘crash’, ‘tumble’, some sort of melodramatic adjective”.

He said: “A lot of the stuff is just within the margin of error. And, honestly, if they had used the same terminology to describe a two-point drop in the sharemarket? There's no way they would be using those words.”

Other subjects covered in this episode of At Large:

• The challenges involved in polling electorates, including Māori seats.
• Curia’s withdrawal from the NZ pollsters’ association. 
• The problems – methodological and legal – about polling during the advance voting period.
• Why it’s all about the trend.
• The time when working with TV3 that he got a poll result he found impossible to believe.