Picking the turning point, the moment when things turn against a government leading to its ultimate defeat, is about as rewarding as a Ken Ring prediction.
OPINION: Of course, if you say it often enough you will be right eventually, but in the interim your credibility suffers every time the predicted seismic shift fails to show.
John Key and his Government have endured a slew of such moments unscathed, but the latest alignment of the planets may be the worst so far, and the latest polls are already beginning to look soggy for National.
The killer mix for every government is a cocktail; unpopular decisions, an electorate tiring of the same old faces and a loss of perceived competence.
Even without the Dotcom cluster-bomb, there has been a catalogue of confidence-sapping events for National; among them the class sizes U-turn, the postponement of the asset sales programme and, most recently - and perhaps long-term the most damaging - the restructuring of schools in Christchurch.
Closing schools is always a fraught issue, as former Labour education minister Trevor Mallard found when he gave it a whirl - and reaped the whirlwind - in Invercargill.
Even if it is done well, it is difficult to overcome the irrationally sad and angry response when what is often the centre of a community is threatened; think post office closures with bells attached.
The demographics may justify it, as they will in some areas of Christchurch, but the evidence still needs to be convincing and the data the Education Ministry is using is clearly not.
Everything from a miscounting of school buildings, a failure to distinguish between slight earthquake damage and serious munting, to outdated data and, in the case of Burwood School, mistaking a long-jump pit for liquefaction.
It will take a lot more than another round of consultation to convince parents and children that the right decisions are being made for the right reasons.
With the class sizes debacle and the compromised national standards data also in mind, Mr Key ought to be regretting promoting Hekia Parata - an awful jargon-fuelled and evasive communicator - into the education role. She makes her predecessor, Anne Tolley, look calm and competent.
By comparison, the Dotcom saga and the role of the Government Communications Security Bureau had been a much more "beltway" issue; until yesterday.
The revelation from the GCSB that, despite his denials, it had "briefed" Mr Key on its involvement in the Dotcom raid (and who can rule out an element of utu after Mr Key's mention of a "brain fade" at spook- central) was bad enough. He will now have to put the record straight in the House.
But its own internal review has also revealed that the bureau, for which Mr Key has ultimate responsibility, also "helped the police" on other occasions involving New Zealanders.
That takes the issue to a whole new level, which requires a closer look not only at the internal competence of the GCSB but also the relationships between the police and the GCSB - and the Security Intelligence Service.
How did it happen that the police more than once went to the GCSB to seek information about a New Zealand citizen?
Or was it a cosy arrangement that avoided the need for a warrant via the domestically- focused SIS?
Mr Key has tried to deflect any personal criticism of his oversight of the bureau, arguing that it would be unacceptable for a prime minister to be involved in operational matters to the extent that he determined who was and was not put under surveillance.
That is true up to a point, but something of a straw man.
In the case of the GCSB, he and Inspector-General of Intelligence and Security Paul Neazor between them are the equivalent of all the select committees, media questions, parliamentary questions and Official Information Act requests that scrutinise every other government agency.
When it comes to the spooks, it clearly requires a more active and careful role by the responsible minister than just box-ticking, policy checking and form-signing. It requires a much greater level of ministerial knowledge of operational matters - and greater checking that the organisations are staying within their brief - when the other external agencies that ensure scrutiny and accountability are sidelined.
It may not suit Mr Key's "chairman of the board" and devolved management style, but he needs to both tighten up his surveillance of the surveillers as well as accept that some of the blame for GCSB's lapses, and the culture that led to them, may lie closer to home.
Disclosure of interest: Vernon Small went to Burwood School and feels irrationally sad that it may close.
- The Dominion Post