We don't get many public opinion polls in New Zealand these days. The ones we do have, however, show the election on an absolute knife-edge. How is that possible, given that we are only in the first term of a prime minister as widely beloved as Jacinda Ardern?

A path to victory in 2020 has always existed for National. However, it is very narrow. To even have a shot, the party needs to win a relative majority of seats and for either NZ First or the Greens (or both) to win none. As of today, that's a real - if far from certain - possibility.

Here are five reasons why.

One: MMP always wins

A key feature of MMP (or drawback, depending on your perspective) is to set the prevailing winds against the single-party rule. While governments have appeared on the brink of an absolute majority at times, it has never quite transpired. And one result of that is that governing majorities are slight even at the best of times.

Think about the elections we commonly consider to have seen the opposition routed. In 2002, Helen Clark had to limp home with the weirdos in United Future for a majority of just two. John Key's dominant performance in 2014 gave him a majority of just four.

But those elections, while close, were also never really in doubt. That's not the case this year, which means MMP can't account for the uncertainty of surrounding this years result. Nevertheless, the closeness of elections now means that there is no safety margin for the Ardern-Peters government.

And that’s a problem for a government not facing a demoralised opposition.

Two: The public never really repudiated the last National government

The popular media narrative about 2017 is that Jacinda Ardern was a kind of Joan of Arc figure who united the disunited peoples of the Left to finally end the "nine long years" and shrug off the yoke of National government. It is a framing that Is very agreeable to many of us in the chattering classes because it validates certain dearly held beliefs about National. It is, however, utterly at odds with the facts.

Between 2014 and 2017, National's share of the vote declined by just 3 per cent. The 44.45 per cent of the vote it won that year is actually one of the best results that any single party has won under MMP. And it was more than seven points greater than what Labour received that year. Pluralities of the vote aren't determinative under MMP - even very strong ones. But it does not follow that they count for nothing. There are all sorts of advantages that are associated with coming first.

Three: National has a local edge

National's commanding party vote victory saw it winning twelve more electorate seats than the victorious opposition did. Electorate MPs and list MPs have the same status in terms of their legislative powers. In individual communities, however, being the local MP still counts for something. It clothes you with a mana that list MPs, whose position comes from party central and not local voters, do not enjoy.

Civil society may not be what it used to, but those columns in the local rag, school prizegivings, honorary Rotary club memberships and radio interviews still add up. A party of community leaders will always have an advantage in visibility and resiliency compared to those more reliant on party apparatchiks.

For some time now, National has had a strong edge in that regard and it shows no sign of going anywhere.

That is just one advantage that flows from National's first place finish in the 2017 party vote. There are others, such as the fact that it is more cohesive as an opposition than Labour, NZ First and the Greens are as a government. That means that National has the luxury of presenting a unified critique of a disunited government’s handing of the most important issues.

Four: Voters trust National on the economy

The economy is in the midst of a slowdown and the ongoing impact of coronavirus will probably have a worsening effect. Voters consistently demonstrate that they care about the economy more than anything else. Rightly or wrongly, they’ve also demonstrated that they trust National on those matters than they do any other party.

Every government thinks it has received a hospital pass from its predecessor. The fact is, however, that the ability of politicians in Wellington to shape the economy is rather limited. Good seamanship will only get you so far and the ship seems to be heading into a typhoon.

Five: Ardern is popular, but it’s not enough

If you were to survey newsrooms and faculty staffrooms around the country, there's no doubt the prime minister would have an overall preferred prime minister rating of around 95%. And because the chatter of those rooms dominates public opinion, you'd be surprised for thinking that's not too far from the mark in the real world too.

It’s not the case.

In the last ten public polls, Jacinda Ardern's preferred prime minister percentages were been 42, 38.7, 36, 38, 38.4, 41, 45, 51, 44 and 41.8 for an average of 41.6. Those are pretty good numbers. They're certainly a lot better than her competition can manage. But for the sake of comparison, here are John Key's last ten numbers to the end of February 2011: 48, 49.1, 49.1, 52, 48.7, 45, 46, 48, 58 and 49.9 for an average of 49.4 per cent.

So while Key never received the same bien-pensant exaltation that the prime minister does, he was more popular at this point in 2011 then she is now. A lot more popular. And he won a majority of three seats.

Ardern remains significantly more popular than Simon Bridges. However, the idea that this assures her of a right to govern is even more tenuous than the idea that the largest party should always be in government. So if the prime minister's personal congeniality is the thin reed of hope Labourites are holding onto, then they might just be in for a rude shock.

National is in with a chance, but there’s no room for complacency

Nevertheless, it remains more likely than not that the government will be returned. If Labour and the Greens outpoll National, which you have to assume is probable, Ardern will remain prime minister. Do not be in any doubt about that.

By rights, however, National should be on the floor gasping for air. The fact that it can credibly talk about the possibility of winning is, on its face, quite astonishing. It also goes to show that, for all his imperfections, Simon Bridges has actually done a pretty good job of holding the party together through some pretty testing times.

And who knows, he just might pull it off.