For two COVID-dominated years, Labour has held sway in politics - including the 2020 election which gave the prime minister a second term with a historic parliamentary majority.

The polls this year tell a different story.

From stratospheric highs, Labour has fallen back down to earth to be in a bunfight with the centre-right National party.

Labour led National in 52 consecutive published polls beginning in February 2020.

National, under leader Chris Luxon, snapped that streak in January this year when Australian pollsters Roy Morgan put it ahead 35 per cent to 33.

The blue side of politics has led a majority of published polls since, including a May poll which stretched their lead to 8.5 points.

"All signs are that next year will be a typically close election," National-aligned commentator Ben Thomas said.

"There's been a steady rise in National's polling since, crucially, the installation of new leader in December last year ... we're seeing the the laws of political gravity kicking again."

Both Mr Thomas and Neale Jones, Ms Ardern's former chief of staff turned lobbyist, agreed cost of living pressures have been central to the turnaround.

"We have a an economy which is at risk of tipping into recession. Things are a bit tough," Mr Jones said.

"There is just a general sense that things are really hard at the moment in New Zealand so you'd expect an incumbent government to be faced with difficulties."

A key proxy for government performance - whether New Zealanders believe the country is headed in the right or wrong direction - is also trending badly for Ms Ardern.

For the first time in her prime ministership, more Kiwis are answering no to that question than yes.

Still, Ms Ardern cast a confident figure when asked about polling this week.

The leader, who celebrated her 42nd birthday on Tuesday, batted away a question suggesting National had momentum, saying it "doesn't square with the polling I've seen".

To a suggestion that Labour was on track to lose seats at the 2023 poll, she responded sharply "Which polling is that?" before ignoring the question.

Ms Ardern may be drawing confidence from preferred prime minister polling, which has her in front of Mr Luxon by a double-digit margin.

Grant Robertson, Ms Ardern's attack-dog deputy, alluded to this in parliament on Wednesday by declaring Mr Luxon's standings dropped five points following a nationwide debate on reproductive rights, when he agreed abortion was tantamount to murder.

"Her polling has come down from its peak but Jacinda Ardern remains an incredibly popular prime minister," Mr Jones said.

"Compare her, say, to Joe Biden, personal ratings are rock bottom and look at what happened in the UK and the departure of Scott Morrison.

"Jacinda Ardern is actually polling very well for someone who's well into their second term and is facing a series of major challenges, including COVID, cost of living and the economy."

The shape of the political contest will come into sharper context in the coming months as Ms Ardern puts a series of international travel behind her to knuckle down at home.

The prime minister spent much of the colder months on the road, with back-to-back trips to Singapore-Japan, the USA, Australia (twice), Europe and Fiji.

By any stretch, those missions have been extraordinarily successful.

In Europe, she sealed a trade deal between the European Union and New Zealand.

In America, she met President Joe Biden at the White House, as New Zealand foreign policy subtly pivots towards the US in the wake of China's tacit support for Russia's invasion of Ukraine.

And in Australia, she won a commitment from Anthony Albanese's government to look at improving citizenship pathways, a move that will grant many Kiwis more rights in Australia, and ease NZ's long-standing deportations complaint.

Mr Jones said Ms Ardern's first overseas travel in two years demonstrated to Kiwis "there's more to her than being the COVID prime minister".

As she steps out of the COVID-19 shadow, Mr Thomas said the government needed to refute the opposition's charges of incompetence to win in 2023.

That means easing cost of living pressures, lowering crime, and landing pledged reforms in health and infrastructure.

"Labour were really in a rut, being accused of failing to deliver prior to the pandemic," Mr Thomas said.

"Once you remove the pandemic response, they're back with the lack of delivery narrative on a lot of key promises. Crime has become more of an issue, and particularly more visible, gang crime and organised crime.

"The nature of MMP elections in New Zealand is that is they are always close, the last election being the exception that proved the rule ... and both parties are now right in the hunt."

Australian Associated Press