All parties poll constantly so they can track public opinion. The overwhelming view, especially over recent months, was that the country was on the right track.
Yet the parties crowded on the left - having largely vacated the centre - insisted that New Zealanders were tired of Key and his colleagues. They sensed a "mood for change" gathering momentum that would lead to a change of Government.
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In the aftermath of what will rate as one of the all-time great election victories, various left party leaders have put their crushing defeat down to the media, Nicky Hager's Dirty Politics book, bloggers, spies, Kim Dotcom, each other, lack of inter-party co-ordination - anything but the fact not enough voters backed them.
Hopefully, once the dust settles a mirror will be available and a serious discussion will begin.
It should start by understanding that in New Zealand politics the foundation for victory is in the centre. A party seeking to form a stable, strong government has to have a message that appeals to around 40 per cent of these voters.
To convince them it will also need to be well organised, well-led and look like it could govern. Voters usually know what is good for them - and it isn't a party that does not look like it can govern itself.
Finally, a major party must be seen to be going in the right direction. It can have great policies and be well organised but it must also "feel" right to voters. Call this a moral mandate.
With a message, an organisation and mandate in place a major party can turn its attention to ensuring it has a parliamentary majority by talking to other parties. Smaller parties approach elections differently. They aim to represent those whose political aspirations are more narrowly focused. Where aspirations overlap, or add to those of the major party, a coalition can form.
Watch: Election 2014: Key 'it was a tough campaign'
None of this happened on the left at this election. Labour moved left to secure what it assumed was its base and never moved back. Over six years it failed to effectively oppose the Government and propose a coherent policy platform that won the support of 40 per cent of voters. It persisted in arguing New Zealand was on the wrong track (which it may well be) when most voters thought the opposite.
In addition, it confused voters by vacillating between behaving like a major party and then like just the largest of a left grouping. When it began arguing that it really was a major party it was too late.
Meanwhile, smaller parties sensed Labour was bleeding and made it sound like they would be calling the shots should a left-leaning government get elected. When the majority of voters are in the centre the last thing they want to hear is that the tail will be wagging the dog.
Running a political party is a highly sophisticated business. But the fundamentals are reasonably simple.
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They boil down to ensuring politicians and their supporters do a lot more than talk to themselves. Left-wing parties would have been getting the same polling data as right-wing parties but they seemed to prefer the feedback they were getting by living in a bubble. They fell into the trap of wanting something so badly they thought voters were thinking the same way.
This is why the result of the election was largely known before the campaign started. The various "sideshows" that emerged could have derailed predictions but in the end they reinforced them.
Of course, what are currently seen as distractions have yet to be resolved and may impact on the next election.
This election was a disaster for the left. But disaster is something all parties experience if they are in the game long enough. Some never recover, others bounce back.
Parties of the left will bounce back if they are prepared to seriously revise their thinking. If they continue to argue that the only problem is that voters do not know what is good for them, recovery will be hard. If revision sees a major centre-left party re-emerge that can look for support to its left and elsewhere, then recovery could be just down the road.
Steve Maharey is Massey University's vice-chancellor, and a former Labour government minister.