Fact or fiction: Is Ardern really the most popular PM in a 'century'?

Is Jacinda Ardern really the most popular New Zealand Prime Minister in a century? Photo / Lewis Gardner

A poll last night revealed what most New Zealanders probably already knew: Prime Minister Jacinda Ardern is a popular Prime Minister.

But for Newshub to call her the "most popular Prime Minister in a century" is "hasty and premature", says a political historian.

In fact, there were no opinion polls before 1974 and the claim compares Ardern's personal popularity to the last century of election results.

The Newshub/Reid-Research poll on Monday showed Labour's popularity soaring to 56.5 per cent while 59.5 per cent said Ardern was their preferred Prime Minister.

It's true that if those numbers were reflected in the voting booths, it would be the biggest majority any party had won since 1908, even eclipsing beloved Michael Joseph Savage's 55.8 per cent result in 1938.

Former New Zealand prime minister Michael Joseph Savage was perhaps the most beloved leader in our history, says a political historian. Photo / NZH Archives

Though opinion polls don't often match the votes and to compare them was "silly", said Grant Duncan associate professor of politics at Massey University.

Ardern hasn't had the longevity of the likes of Savage nor comfortably won an election. And the poll was taken in an unpredictable and extraordinary time, he said.

"It's silly to say at this stage, let's just wait for six years before we make that claim.

"Let's hold the horses, please."

Despite Ardern clearly being popular and doing a great job, the tide of public opinion might turn come September when the pain of unemployment peaks and a $50 billion debt needs to be paid back, Duncan said.

"And what goes up, must come down."

But the claim of "most popular Prime Minister" is true when it comes to the Reid-Research poll, which has been around since 2009.

Though it's incorrect when other polls are taken into account.

Former New Zealand prime minister Sir John Key, here with Governor-General Dame Patsy Reddy, has polled higher than Jacinda Ardern and was knighted. Photo / Peter Meecham

For example, then Prime Minister John Key's preferred prime minister ranking reached as high as 73.3 per cent on a Herald-Digipoll in 2014.

In fact, Key consistently polled around 60 per cent in Herald-Digipolls during his tenure as prime minister and in September 2011 peaked at 59 per cent in the 1 NEWS Colmar Brunton poll.

What's more, New Zealand's first opinion poll was the Heylen poll taken on September 15, 1974, meaning popularity of the likes of Michael Savage or Norman Kirk can't be taken into account.