At a stroke, the election has become a referendum on genetic modification.
But it has also become a referendum on whether the minor party tail should wag the major party dog.
The Greens have delivered an ultimatum to Labour - promise to extend the moratorium on the commercial release of genetically modified
organisms beyond October next year or wave goodbye to any chance of forging a post-election coalition agreement.
And should Labour try to run a minority Government and then drop the moratorium, the Greens would pull down that Government.
It is high-risk stuff.
For the Greens, it is simply their bottom line - a point of fundamental principle upon which they cannot buckle. If they don't make a stand on this issue, then they don't stand for anything.
It is arguable whether this ultimatum will win them more votes. Greater clarity of their stance may cement support; dogmatism of this kind may loosen the attachment of those who initially saw the Greens as fashionable, but who might now find them just plain scary.
It is a big gamble because left-leaning voters might simply punish the Greens big time for trying to hold an ally to ransom.
The ultimatum might also give Helen Clark another reason to go to the country early to seek a fresh and clear mandate.
Above all, the prospect of the bolshie Greens setting non-negotiable bottom-lines might help Labour succeed in its intention of running a standalone Government after the election.
With National seen as having no chance of winning power, some National-leaning voters might now prefer to help Labour rule alone rather than see a moderate centrist Government being forced to make concessions to an inflexible, minority coalition partner on its left flank.
Perversely, that might suit the Greens. Having seen the dreadful experiences of the Alliance and New Zealand First as minority partners, the Greens have displayed severe qualms about going into coalition.
A definitive position is due to be hammered out at the party's annual conference at Queen's Birthday Weekend.
With the polls already pointing towards a Labour majority, the voters may now solve the Greens' dilemma for them.
