But that's not to say an election cannot be turned on its head, and its outcome influenced, by an issue that emerges from the shadows and takes over the campaign agenda.
In 2002 Helen Clark's government was seemingly cruising to victory, despite its social democratic policy agenda having riled big business. Labour was poised for a possible outright majority.
In the run-up, Labour and the Greens had niggled over genetic modification issues, and sections of the public were disquieted, too. But nothing serious enough to define the election. Then two weeks before polling day came the "Corngate" affair.
Clark was ambushed in a television interview with allegations — contained in a book by investigative writer Nicky Hager — that genetically modified corn seed had been imported and planted. A media feeding frenzy followed as claims of a cover-up were strenuously denied.
In the blink of an eye Labour's support slumped from 50per cent to the low 40s. On election day Labour limped home with 41per cent of the vote (aided by National tumbling to an historic low of 21), forcing Clark to cobble together a governing arrangement with three other parties.
Then, in 2005, Labour was on the skids, with Don Brash's National Party holding an 8 to 10-point poll advantage as the election neared. But in mid-campaign Brash was derailed by the Exclusive Brethren affair, which saw him being forced to backtrack on a denial that he knew the church was distributing anti-Labour leaflets.
Fitness to govern became an issue and Brash was deemed too risky, so costing National the election.
Fast forward to the present and reflect on what is happening in midterm elections in the United States.
As I observed on a visit stateside this month, the issues troubling Americans have a familiar feel: fears of global recession, energy insecurity, rising interest rates, high inflation. The early predictions were for sweeping Republican gains in the midterms, on the back of these economic woes.
But the US Supreme Court's decision in Dobbs v Jackson Women's Health Organisation in June, overturning the constitutional right to abortion enshrined by Roe v Wade 50 years ago, has been a gamechanger.
Suddenly the contests for some congressional seats and governorships look more evenly balanced, as the Dobbs decision motivates liberal voters.
In some outlets, wrangling over abortion rights gets as much air time as the economy.
Media are reporting a surge in registration among enraged women. And the Democrats' election machine is leveraging their fury by targeting the wackier and more extreme pro-life Republican candidates.
They have some rich pickings.
Herschel Walker, an ex-football star whose challenge to a Democratic senator in Georgia is crucial to Republican ambitions, is a pro-lifer who supports a total abortion ban. The trouble is, he's making headlines after it was revealed that he paid for a girlfriend's abortion in 2009.
The Democrats' television advertising is brutally direct. In one spot, a woman who experienced a pregnancy-related complication, requiring her to have an abortion, says that that wouldn't have been possible had the New York Republican candidate Lee Zeldin been governor at the time.
"That's why Lee Zeldin scares me," the woman says, eyeballing the camera. "He'd ban abortions without exception for rape, incest or lives like mine, that's so cruel. He's too extreme, he can't be our governor."
Watching this issue play out in the United States prompted a thought about the possibility that abortion resurfaces as an issue for New Zealand voters in 2023. The Dobbs decision generated discomfort for National in mid-year, especially leader Christopher Luxon, a fundamentalist Christian and pro-lifer. His opponents will have filed that away for future reference.
Luxon has pledged that a Government he leads won't revisit abortion laws. But he's dogged by his response to an interviewer's "abortion is tantamount to murder" line, having admitted that the statement embodies a pro-life position. So we can expect his pledge to leave abortion laws untouched to be further tested at some future point.
Luxon's personal poll ratings climbed in the first half of the year, but stalled after he scrambled to issue three statements in 24 hours as the Dobbs decision caused him and his party some uneasiness. It became clear that many people, mostly younger women, had been destabilised by his prevaricating.
Will abortion be a gamechanger issue in election year? Probably not, but it could be used to raise questions about what the National leader truly stands for. Luxon's tightrope walk on the abortion issue sees him trying to avoid saying things that he believes but that he knows are politically unpalatable.
That's the thing about elections. Issues can suddenly arise that give us new insights into the key players. And issues that have lain dormant for a while can suddenly return with a vengeance.
These are tumultuous and fast-moving times as restive populations struggle to cope with economic hardship, an as-yet-untamed pandemic, global disruptions triggered by war in Europe, and rolling natural disasters brought on by a rapidly warming planet.
All of the above will probably still be preoccupying voters a year from now as they prepare to cast their ballot. But it could be a homegrown issue that nobody saw coming.
All we can expect is the unexpected.
- Mike Munro is a former chief of staff for Jacinda Ardern and was chief press secretary for Helen Clark.
