Do the polls one month out foretell the election result? Here’s what recent history tells us

There is plenty of campaign to go, but the last four elections suggest nothing tends to change too much from here.

The campaign is in its second week of open slather and within 12 hours we’ve had two major polls pointing to two major parties looking decidedly un-major. 

But, hey, there’s a month to go, things could move dramatically. Or could they?

In an earnest attempt to answer that question, we’ve looked at how polling a month out compares with the final result across the last four elections.

Here’s how it looked on Tuesday, when two polls were published: Reid Research for RNZ and Verian for 1News. This is the average.

Let’s roll back the election years and see how it stood at the same juncture. 

To keep it as apples-with-apples as possible, the criteria are these: take the Reid Research polls and the Verian (formerly Kantar and before that Colmar Brunton) polls that were in the field in the fortnight leading up to that month-out mark, and average them. 

Here’s how those numbers compare with the election results in 2023.

Here – and it’s impossible to say with any certainty whether any shift is down to the relative performance of parties or the vagaries of the polling – the numbers of a month before October 14, 2023 are strikingly similar to the election proper, with National’s 1.9-point fall making it the biggest mover overall but Act (down) and NZ First (up) shifting further proportionate to their totals. 

Wind back a further three years and here one result stands out: National had averaged just over 30% a month before the October 17 election – higher, notably, than it is today. Its final result, in that strange Covid-delayed campaign led by Judith Collins who’d inherited the job at the 11th hour, was under 26%.

In 2017, Labour put together a government despite finishing second behind National in the September 23 election. It felt like a tumultuous time – Jacinda Ardern had become Labour leader at the start of August – but the polling from a month before the election is not a far cry from the result itself. The biggest mover is Labour, down by 1.3 percentage points.

How about 2014?

This was the election of Nicky Hager’s Dirty Politics and Kim Dotcom’s Moment of Truth”. For all the turbulence, the two big parties finished up pretty close to their final totals. 

The Greens and Internet Mana were down and NZ First finished a full three points higher than the polls measured a month before. 

The “Con” in that chart above, if you weren’t there at the time, is Colin Craig’s Conservative Party, which came just 1.03% from making parliament.

Where does that leave us? Well, it suggests that the polls of this week are a strong indicator of how it will go on November 7.

Across four elections, Labour and National have both failed to improve on their polling one month out, with the sole exception of National in 2017, when they were up by an insignificant 0.7%.

National took the biggest dive: down 4.7% across that period in 2020. But generally there’s more bouncing around in the smaller parties. The biggest rise on the month-out number across this period is New Zealand First, up three points in 2014. 

But even absent any unusual surge in either direction – and let’s not get into the overhang possibilities now – the composition of parliament is an open question. If you’ll forgive the thunderingly unoriginal observation: a month out, this election looks like being very, very close.