There's rarely one moment when you can say a campaign has been won or lost.

Usually it's a symbolic sign of what is already known - Sir Rob Muldoon's woozy announcement of the "schnapps" election he was doomed to lose springs to mind among those of a certain age.

In the much less nation-shaping context of the Green co-leadership race that saw newbie MP James Shaw triumph on Saturday, the symbolic moment came early on. During a rapid-fire question and answer on the economy on TV3's The Nation, Shaw got the easiest question.

What was unemployment?

He said it was "just over 5 per cent" when it was 5.7. Rough enough.

His main rival, and the early front-runner Kevin Hague, was asked what growth was and said it was "tiny - 0.25 per cent over the last year". Way wide of the mark.

It was 2.9 per cent. It was a clear black mark against Hague and odd given he has a strong business background and is no slouch intellectually or on the economy.

But for someone who has sat through years of debates in and outside the House it was a telling lapse.

There is little more fundamental about an economy than its growth rate, however you measure it. In a race, defined by the media and many in the party, about the need for economic credibility in the Green leadership, it winged Hague badly.

Outgoing co-leader Russel Norman rightly was given the credit for mainstreaming the Greens' economic message.

To be fair to the late Rod Donald he was adept in that area too, but somehow his efforts with business leaders and his penetrating questions at the finance and expenditure committee never gained cut-through - and never really put in the shadows the image of a man in braces pulling publicity stunts to raise the Green profile.

That lack of cut-through may have held the Greens back - that is certainly the received opinion these days, though at the time the Greens were struggling for the oxygen of publicity and Donald was credited with providing much of it.

Either way under Norman and Metiria Turei's watch the party has jumped from around 5 per cent to around 10 per cent and plateaued there and Norman's sober-sided and level-headed economic message deserves much of the credit.

When it comes to politics, New Zealanders do listen to the views of business probably more than comparative countries - and they listen with respect.

If you need proof of that, throw your mind back to the so-called Winter of Discontent in Helen Clark's first term of government when after a successful election Labour's popularity went into serious decline under the implied threat of a capital strike.

It only recovered after a "smoked salmon offensive" by Labour that assuaged business concerns.

Given Shaw's background in business, and his comfort with talking market economics, he was already on the front foot before Hague's lapse on The Nation.

He is also exceptionally witty and quick-witted.

The one thing that could have potentially held him back was a widespread perception both among the media, his colleagues and the party at large that rightly or wrongly he was somehow more sympathetic to dealing with National than his rivals; that he wanted to shift the party towards the centre and towards a stronger emphasis on environmental issues and less on Left-leaning social issues.

It is a favourite theme of conservative commentators that the "right" Green leader would be able to shift the party's emphasis towards the environment and make it a potential partner in a future National Government.

It's an odd but persistent view, given the gulf between the Greens and National is probably wider on environmental issues than in almost any other area.

The real question has always been what would the Greens do if both a Labour and a National government were options and they had the deciding vote.

While the answer is and has always been "Labour", the question is moot - and Shaw made it clear that was his answer too.

Shaw responded early in his campaign to being typecast as "National friendly" - in fact after he had signalled he would not be in the race but before he formally launched his campaign - with a strong effort to disabuse reporters (including this one) and others of the error of their perceptions.

Once that issue was put to bed, he quickly became the favourite as the contender who could expand the Green vote beyond its new plateau - a favouritism that few including the contenders probably picked up ahead of the vote, though it was known to be close going into the weekend.

It remains to be seen if Shaw can lift the Greens beyond the 10-11 per cent range and deliver on the 14-15 per cent the polls occasionally tease them with.

If it's any guide there is a view within Labour that Shaw will likely be a stronger rival than Hague for the votes in play between the two parties.

But at the same time he will help the combined anti-National bloc present a more unified and credible front in 2017.

It's a harsh judgment on Hague who has proved himself an adept politician, but the Greens may not be the only ones who gain from Shaw's victory.