To change a government, voters must perceive it as comical or corrupt, a test the Ardern regime passed with flying colours from the get-go.
But voters also need to feel safe picking the alternative, a test National has yet to meet. After a good run since January, National bumped itshead on a glass ceiling of around 40 per cent and has started sliding in the polls.
When National peaked in April and May, polls indicated that new leader Christopher Luxon had won back more than 400,000 voters who had stuck with Bill English in 2017 but defected to Jacinda Ardern in 2020.
Since then, around 150,000 have returned to Labour. If you are a faithful voter for Labour, National, Act or the Greens, you may think your vote counts. But it is these more promiscuous voters who decide elections.
They flirted with Luxon through the autumn, but headed home to the comfort and safety of Ardern for winter.
To be charitable, these 150,000 are best described as low-information voters.
They have been impressed with images of Ardern parading around the world. It doesn't matter to them that her foreign policy has swung wildly since May, from American toady to Chinese dupe and every stance in between.
Yet don't mistake them for Jacindamaniacs. They weren't impressed by the media's love-in with the new Labour leader in 2017 and stuck with English that year.
They are fully aware Ardern's Government couldn't run a bath, even as they accept the Prime Minister's assurances that it would have been beautifully warm and bubbly had one of her ministers remembered to put in the plug.
They backed her in 2020 because of her leadership through Covid and National's mess, and some to reduce the influence of the Greens.
Once an apparently plausible National leader emerged in Luxon, they gave him a decent look. They now tell pollsters they'll give Ardern another chance.
Responsibility lies with Luxon.
Since taking over, he has offered nothing new.
There were not the Nicola Willis-written re-positioning speeches that John Key offered in 2004 to explain how his Government would be different from the flintier vision his predecessor Don Brash had offered.
As leader, Luxon's only substantive promise has been to cut taxes, including indexing tax thresholds against inflation to help the middle class, but also abolishing the top 39 per cent tax rate on incomes over $180,000.
Labour has delighted in repeating that the latter would give the chief executive of Air New Zealand an extra $270,000 a year and a Prime Minister Luxon around $18,000 more — campaign slogans it is confident would assure Ardern of a third term.
Luxon has also had trouble reconciling his view that loosening fiscal policy through spending is inflationary but through tax cuts is not.
Voters supported Brash and Key's tax-cut packages in 2005 and 2008 because they were offered in the context of record surpluses. In 2023, Labour's claim that Luxon would be borrowing for his own tax cut really would be true.
Willis, Luxon's deputy and finance spokeswoman, wisely downplayed those original promises.
According to Willis, that first Luxon tax plan was just "a proposal for the 2022 Budget".
Willis says she'll provide a fully costed fiscal plan before the next election that will "take into account the economic conditions of the day and the extent of Labour's reckless spending".
The tax component, she says, "will respond to the fact that inflation has pushed people into higher tax thresholds" and that "inflation indexation remains a key commitment of any future tax plan".
She is not quite as clear about whether abolishing the 39 per cent top rate will feature again.
There is a bigger anti-abortion bloc in New Zealand than Wellington cub reporters understand. In any case, the media coverage it generated ensured Luxon's commitment to no change was well and truly heard.
Probably more damaging was his claim that New Zealand businesses are soft, which was heard by sole traders and SME owners who have battled through Covid as applying to them.
They might legitimately ask if the softest corporate job in New Zealand is the one Luxon himself held: chief executive of a state-owned airline that gets bailed out each time it goes bust.
Key was so transparent about his family holidays in Hawaii that his son published videos from the beach on social media.
Whether intentional or not, Luxon instead looked dodgy when his own social media feeds suggested he was hard at work in provincial New Zealand while he was taking a well-earned break in Waikiki.
None of this is fatal, but Luxon's lack of general knowledge of New Zealand over the 16 years he was out of the country, from 1995 to 2011, is a handicap in understanding the context of accusations and events.
That's a problem not just in media interviews and speaking engagements but also, insiders say, in policy discussions with his team.
Labour is raising fears about Luxon to hold on to and attract back support. National can play the same game, asking what a third-term Ardern Government would look like, dependent for every vote on the increasingly more radical Greens and every one of the five Te Pāti Māori MPs.
Nevertheless, unless National starts passing the test of making swing voters comfortable with what a change of government would mean, any fear campaign based around the Greens and Te Pāti Māori risks having the same effect as in 2020, when National voters switched to Labour to reduce the influence of those radical forces on Ardern.
Poor Luxon looked miserable with Ardern in Samoa this week. Perhaps he recalled when he was the Herald business leader of the year in 2013 and chairman of Ardern's Business Advisory Council, charged with helping her do a better job.
As he sat glumly in the second row, with Ardern taking the lead, was he wondering what he has got himself in for?
The election looks set to go right to the wire with the more experienced and nimbler political operator likely to have the edge.
National is stuck with Luxon until then. But unless he has a lot more in the tank than is apparent so far, he's starting to look more like a Todd Muller or Andrew Little than a Key or Ardern.
- Matthew Hooton is an Auckland-based public relations consultant.