By way of proving his point Key opted to compare 100 per cent Pure to the McDonald's slogan: "Lovin' it." He carefully pronounced it sans 'g' just like in the ad. It was doubtful, he added, that everyone who ate McDonald's really was "lovin' it" the entire time they were eating it.
Possibly he chose that multinational conglomerate for the pure fun of watching the left hiss and spit in horror at his gall in likening NZ's environment to a Quarter Pounder. The comparison caused some consternation. Labour leader David Shearer put it most succinctly in a return to unintelligible form after the alarming focus he showed at Labour's recent annual conference: "We have to work much harder at getting our 100 per cent pure really 100 per cent pure, rather than looking at McDonald's and saying 'gosh, there's something like McDonald's rather than 100 per cent Pure."
There were revelations Key was similar to a McDonald's burger this week - Key stood accused of excess cheese, because of the number of photos of him smiling in newspapers last election campaign.
That came in the release of a study by Massey University's Claire Robinson, who assiduously counted, measured and assessed the impact of photos of Key and his rival Labour leader Phil Goff in four major newspapers, including the Herald, to see who fared best.
Robinson concluded Labour and Phil Goff were entitled to feel hard done by - in the four weeks before the election, there were 138 photos of Key compared to 80 of Goff, and the photos of Key tended to be more positive and larger than those of Goff.
Any peer review of the rigour of the study shall be left to others more qualified in the art of academia. But some issues immediately spring to mind.
One is that whether a photo is construed as positive or negative is a rather subjective thing. For example, the study did not take into account the accompanying story or even the headline and it came as a surprise to learn that photos of John Key and John Banks during their infamous cup of tea were considered "positive" for Key in the study - purely because Mr Key and Mr Banks were smiling in the photo.
Even Key disputed whether that was positive, observing he might have had the numbers on Goff, but he was playing at a handicap because many of his photos featured John Banks beside him.
People can be cruel, and after the study was released one wag on Kiwiblog pointed out Goff's 80 photos amounted to 80 more than his own party deigned to put on their billboards, which were free of the usual photos of a leader.
Another, more vicious wag also claimed that the very lack of photos was positive for Goff - putting up the theory that had Goff been given the same coverage as Key, Labour's vote would have collapsed even more.
The other issue is that it is hard to take a photograph of something that is not happening. As one of those on the ground with Key and Goff throughout the campaign, it is arguable that the photos reflected the respective demeanours of the two men at the time. Goff's campaign focused on the anti-asset sales message rather than the walkabouts Key focused on, and so his default disposition was one of righteous wrath rather than smiles. As well as that the polling ensured that for all his attempts to put a brave face on it, Goff was effectively a dead man frowning. In McDonald's lingo, he was the Grimace incarnate of the campaign trail. He knew - and everyone else knew - he was there for a limited time.
By comparison, Labour did not give Key the nickname "Smile and Wave" for nothing. Sour cups of tea aside, he had gorged on Happy Meals - and the polls certainly ensured Key was lovin' it.