As British prime minister, Harold Macmillan was once asked what was the most likely thing to blow a government off course. "Events, dear boy, events," he famously replied.
John Key and Steven Joyce, his Transport minister, would not argue with that maxim.
When it comes to election campaigns - and this year's has effectively, if unofficially begun with the leaders already traipsing around the country - expect the unexpected. Like a 40,000-tonne cargo ship inexplicably wedging itself on a well-charted reef and disgorging tonnes of heavy, fuel oil and shedding scores of containers.
Or - as happened in 2002 - accusations of a cover-up by the Government of imports of genetically-modified corn seeds.
That "event" came out of the blue and threw Labour's campaign well off course.
It was arguably a major factor in thwarting Helen Clark's hopes of Labour governing alone after that election.
National eschews such talk, even though the polls suggest it may be better placed to pull off such a coup.
Once again, however, the vulnerability of incumbency has been exposed. The unfolding ecological disaster in the Bay of Plenty illustrates how quickly the advantage National enjoys as the governing party heading into next month's campaign proper could melt away.
National's problem is that the margins between governing alone, governing with allies and not governing at all are not that large.
The MV Rena has been the only salvage operation in town.
It has taken a lot of talking in a lot of media by Mr Key, Mr Joyce and latterly Environment Minister Nick Smith - three of National's best communicators - to stop the stranding of the Rena becoming National's equivalent of Corngate.
National found itself charged in the court of public opinion with failing to respond quickly to something which was obvious to everyone else - that the ill-fated ship was going to break up and cause New Zealand's worst marine environmental catastrophe. Obvious in hindsight, that is.
The exception was Gareth Hughes, the Greens' marine spokesman, who agreed earlier than most with Mr Joyce the ship could break up. Mr Hughes was quick to put Mr Joyce on notice for the supposed slow reaction of Maritime New Zealand.
But not as quick as the Greens would like people to believe.
The fate of the Rena was such a pressing priority for the Greens that they did not see fit to set down a parliamentary question to Mr Joyce on the Thursday before last even though the Rena had struck the Astrolabe reef some 36 hours earlier. Mr Hughes was instead on the case of another navigation-challenged wanderer of the high seas, quizzing Fisheries Minister Phil Heatley as to whether the Emperor penguin Happy Feet had come to an unhappy end as by-catch in the net of a sub-Antarctic trawler.
While Hughes was otherwise engaged, the preliminary stages of what will be an intensely complex salvage operation were already well under way in part because Mr Joyce had given the ship's owners the hurry up.
The recent cross-party negotiations which resulted in much-improved emergency legislation restoring the police's ability to use video surveillance was MMP politics at its best.
The grounding of the Rena has spawned a bout of MMP politics at its worst, with opposition parties trying to chip away at National's reputation for competence in disaster management.
They have sought to capitalise on public anger at the seeming slow progress in removing the oil from the ship by playing a crude blame-game to find a political scapegoat - in this case either Mr Joyce or Mr Key or both.
National's opponents were simultaneously clambering over one another in a game of policy one-upmanship in pursuit of the most populist position.
The beach at Mount Maunganui has not only been ankle-deep in sticky black tar. It has been knee-deep in politicians.
Phil Goff, at least, showed some restraint in delaying his visit. He then blew it by calling for a moratorium on new deep-sea oil drilling until suitable environmental safeguards are in place. He may have only been matching the Greens. But this was policy-making on the hoof pure and simple.
This political circus has not been bothered with the letting the facts get in the way.
The facts were, however, that it would not have made any difference had a vessel been available earlier to offload the 1700 tonnes of fuel oil on the Rena. The poor condition of the fuel tanks and pipes on the Rena was such that marine engineers could not start pumping fuel out of the ship until last Sunday night. The operation continued through Monday before the weather worsened. The Rena shifted, sustaining further damage.
Oil started leaking in serious fashion.
The rest is history.
National's problem, however, is that despite the facts, the Government is perceived to have acted too slowly. And perceptions, once established, are hard to eradicate. Where the Government fell short - and what cemented the perception that not enough was being done - was a failure to communicate strongly enough in the early stages what was actually being done.
Unlike Pike River and the Christchurch earthquakes, the prime minister did not drop everything and fly to Tauranga the moment he was told the Rena was stuck hard and fast.
But then no-one had died and Maritime New Zealand had activated its crisis response procedures.
Had Mr Key done so, it would have been a symbolic gesture which would have said "it's all under control" and "we're here to help".
The question is in what circumstances the prime minister draws the line and simply allows officials to get on with the job without having to accommodate flag-waving exercises by their political master.
The hullabaloo over the handling of the Rena is further evidence that nothing is exempt from the piranha-like feeding frenzy induced by too many parties chasing too few votes.
The job of prime minister has accordingly become four-fifths short- term crisis management and one-fifth long-term vision - instead of the other way around.
- John Armstrong is The New Zealand Herald political correspondent.
