‘Nine long years’ is a jazz standard in political debate. Using opinions and mathematics Toby Manhire has settled on the moment from which it is no longer acceptable to use this rhetorical device. No correspondence will be entered into.

The rule is simple: everything good is down to the current government, and everything that isn’t good is down to the last government. It’s as true today as it was under the last government. Unless you happen to be the opposition, in which everything good is a legacy of the last government and everything that is not good is a result of the current government pissing all over the paradise they inherited.

The most familiar refrain here is nine long years – throughout the Key-led government this bounced around the parliamentary chamber like a beach ball. It may be true that there was a Marmite shortage, but didn’t Labour have nine long years under Helen Clark to ensure Marmite supplies, etc, so on, &c.

These days, sure as night follows day, it’s Labour grasping at the same line. You might criticise what’s happening in housing/health/schools/All Blacks, but National had Nine Long Years to put housing/health/schools/All Blacks right, etc, so on, &c.

The flipside of that coin, particularly in the early years is, of course, the claim for credit – so, from the National benches, understand this: the strong economic numbers are 100% down to the last government’s stewardship, thanks and bye and please show yourself out.

The point is: it’s all a bit of a bore and a diversion and at some point we must as a nation stand up like Twisted Sister and say we’re not going to take it any more. We must divine the cut-off, the moment beyond which saying “blah blah long years” or any variation thereof is verboten.

But when should that cut-off be?

“I guess about one year in to the second term,” said one Labour cabinet minister. “One term,” said a National frontbencher. “About one term.”

Two years, said former Māori Party co-leader Marama Fox. “Sadly that’s how long it will take new ministers to get their heads around the job – unless you’re good then you just get on and deal with it. Sad but true.”

Let’s cross to Wayne Mapp, a minister in Key’s government. “Up to about two years, though it gets tired after even one year,” he said. “Steven Joyce used to say for the first term you could blame a lot on the previous government, but you couldn’t get away with it in the second term.”

If I recall correctly that didn’t stop him.

“This isn’t a science and there are no hard and fast rules,” said former Boss of the Press Gallery Linda Clark. “The ‘responsibility off-load’ is merely a deflection technique. Its ‘successful’ delivery (or not) will depend on the skill of the politician using it.”

John Key, and especially Steven Joyce, were “exceptionally skilled at deflecting responsibility”, she said. “Part of Key’s skillset was he did this while never coming over as bitter or cross – voters were more willing to accept (or at least not reject) the deflection on those terms. Under Key, voters accepted that issues were hard, tricky, intractable – all reasons to lower expectations of what the government could do or what responsibility it had in practice. (Think GFC.)”

Great points all, but when is the cut off, Linda Clark?

“Labour can rightly deflect responsibility at this stage of their first term,” she said. “With only one budget locked in, and not yet fully executed, this government (like any new government) is still managing the circumstances created by its predecessor. My best guess is that Labour will not be given the same license to deflect responsibility for as long as Key’s government. Labour governments traditionally have to work harder than National government to prove themselves as prudent or reliable managers; the hard-wired assumptions that Labour governments tax and spend will undermine any deflections and certain Labour ministers will struggle to deflect without appearing angry or oppositional to the previous administration.”

More great points. But when is the cut-off? When?

“If you have to say how long can they blame the other lot,” said Linda Clark, hovering towards a definitive ruling, “it depends on the issue.”

Damn it. “For example, and in very general terms, longer on issues like climate change, education and health (issues where voters may tend to see Labour as credible), but less long on issues like RMA, immigration, employment (where, arguably, National is more likely to be seen as credible). The Interesting thing for me is that on the really hard stuff (eg housing or pay for teachers or construction industry issues) the ‘who’s fault is it really’ trope locks both sides into a side show of finger pointing that ultimately turns off voters. These are issues we all want to see solved; looking back to sheet home blame is unlikely to move anything forward.”

Intelligent but utterly unquantifiable nuance. Next!

Peter Dunne, who was a minister for a thousand years and an MP even longer, will deliver. “New governments can heap all the blame they wish on their predecessor without limit for the first year,” he said, with the crisp authority for which he is rightly famed.

“Once they produce their first Budget, they are free of the previous government’s policy and fiscal settings, and are then on their own, so the blame game is a little harder to sustain. Then it becomes a matter of what specific policies they have introduced or are planning to introducing to overcome the perceived shortcomings of the past, and how they are working. By the end of the first term, it is starting to stretch credibility to blame the previous government for all the country’s problems.”

He had a caveat. “There is a distinction between blaming the previous government for what it did, and blaming it for what it did not do. While the three-year horizon referred to above probably covers the ‘what it did’ situation, the time frame for the ‘what it did not do’ criticism is far more elastic, limited only by the public’s willingness to accept the criticism.”

We needed someone above all the hurly burly, from the academy. “I think they are entitled to one term,” said Jennifer Curtin, professor of politics and international relations at the University of Auckland. “The reality of the mechanics of policy change, especially significant redirection, would mean that it takes at least three years in any system to see implementation of new work impact outcomes. Especially if the government before had been in for a long time and had embedded policies that a new govt wants to change. Unless of course a government emulates the fourth Labour government’s speedy approach, which most recognise is suicidal politically.”

Thank you, professor. We’ll put you down for one term.

And finally to Neale Jones, formerly chief-of-staff in the Labour leader’s office, now a PR flak stalking the Quays of Wellington. “An interesting topic, and one that as a former opposition staffer I am very familiar with,” he said. “There was a certain absurdity to being attacked for the record of the Clark government well into National’s third term.”

Not that Key invented the tactic, he acknowledged. “Tarnishing your predecessors’ record is a tried and tested political strategy. It works for a while, and for good reason. Kiwis understand that governing is like turning an ocean liner around, things can’t be done overnight. That’s why historically governments in New Zealand have tended to get at least two terms.”

All right, all right. When is the cut-off!

“The blame game works until your government has had a reasonable opportunity to address the social or economic deficits they’ve been left by the last lot. Most people understand that one term is not long enough to do much of anything. By your third term people expect you to have addressed any problems you were left, and these problems are well and truly your own. So I would say the licence to blame the other side probably expires some time in the second term.”

A little vague, but we’ll put you down for four-and-a-half years.

So where does that leave us?

Labour minister: 4 years

National frontbencher: 3 years

Marama Fox: 2 years

Wayne Mapp: 2 years

Linda Clark: !?

Peter Dunne: 3 years

Jennifer Curtin: 3 years

Neale Jones: 4.5 years

Average: 3 years and 26 days

So there you have it. The countdown begins. The countdown until November 21 2020, three years and 26 days after the swearing in of the Labour-led government.

On your marks.