Six weeks ago, New Zealand’s election campaign was limping toward a foregone conclusion. The centre-right National party looked a shoo-in for a fourth term (matching the legendary 1960-72 administration of Keith Holyoake), and prime minister Bill English was on track to find redemption (he was party leader when National suffered its worst-ever election defeat in 2002).

New Zealand election 2017: record early voting as Ardern and English fight for win – live Read more

The most recent polls suggest that both of these things may well happen. But in every other respect New Zealand’s domestic politics have been transformed.

Pivotal developments, highlights and lowlights

After a string of poor poll results, Andrew Little stepped down as leader of the Labour party on 1 August. The deputy leader, Jacinda Ardern, stepped up to the plate. Everything thereafter hinged on this moment.

Mark Richardson, an ex-athlete masquerading as a political commentator, asks Ardern whether or not she plans to have children. Ardern’s response leaves Richardson spluttering and galvanises an awful lot of people who thought that kind of misogyny had been left behind in the last century. Ardern also galvanises the National party, which realises it has a fight on its hands.

Ardern generates a new line in neologisms, including such gems as “the Jacinda Effect”, “Jacindamania”, “Jacinderella”, “The Jacindanator”, and (my favourite) “Jacintime” (although this one is looking a little optimistic).

Four leaders’ debates take place. English steadfastly refuses to even look at his opponent. Ardern more than holds her own.

The Ardern effect begins to wear off when finance minister Stephen Joyce claims there is an NZ$11.7bn hole in Labour’s sums. Despite the fact that no credible economic commentator on the left or the right thinks this is correct, English and Joyce keep on message. The mud sticks.

Labour has tax issues. Early on Ardern made a “captain’s call”, indicating that she would set up a tax working party if Labour was elected. This group might (or might not) recommend a capital gains and other taxes, some or all of which might (or might not) be legislated before the next election in 2020.

Ardern is eventually forced to clarify that any new taxes recommended by the working party will be put to the public in 2020. But the damage is done. No matter that National has introduced in the vicinity of 18 new taxes since it took office in 2008, some of which were not signalled during election campaigns. No matter that New Zealand is one of the very few countries without a capital gains tax – and home to some of the most unaffordable houses in the world.

A farmer protesting Labour’s planned water tax holds up a placard describing Ardern (not English) as a “pretty communist”.

Stability vs change

Nearly one million people have already cast advance votes. This represents roughly half of the total turnout in 2014.

On polling day, New Zealanders face a simple choice. National is going hard on a stability and continuity line. Labour is looking for a generational step-change and a new style of politics.

Ardern promised an “unrelentingly positive” campaign. English, on the other hand, has run a campaign designed to paint Ardern and Labour as a risky proposition.

Is it working? Labour’s polling, and Ardern’s numbers as preferred prime minister, have fallen away a little recently and some polls are pointing to a National victory. However, there remains the matter of forming a government which, under New Zealand’s version of proportional representation, can be an unpredictable kind of affair.

National may well win a plurality of all votes and hold the lion’s share of parliamentary seats, but that does not guarantee that it will retain the treasury benches. Unless it wins a parliamentary majority in its own right (and New Zealand hasn’t had a single party majority government since 1994) it is going to have to form an executive or legislative coalition with another party. Its natural allies are dropping away at an alarming rate.

In particular, if the faux-populist New Zealand First drops beneath the threshold (either 5% of the party vote or a single constituency seat), National is in trouble. Were that to occur Labour and the Greens could well form a coalition administration (perhaps with the support of the Maori party), even if Labour wins fewer seats than National.

Beyond the question of who forms the next government, however, New Zealanders will look back on this election campaign as a turning point.

One way or another, the 2017 general election will always belong to Ardern. In the space of seven weeks she has managed to bring the Labour party back from the brink (with an honourable mention to Little for his courageous decision), electrify the campaign, and force National to actually do something.

Perhaps most importantly, she has shifted the political centre. New Zealand has had nearly four decades of numbing neo-liberal orthodoxy in which the state has been maligned and markets routinely held up as the best instrument for dealing with policy challenges. Ardern has challenged that by positioning the state as a force for imaginative and positive change.

Ardern has left National looking old, tired and bereft of genuinely new ideas. Not a bad first-time effort for a “pretty communist”.