Claire Trevett: When it comes to the Greens size does matter to Winston Peters

The Green Party has always had long and convoluted processes to make decisions around anything from a leadership change to changing a toilet roll.

It prides itself on its democratic processes, the power it devolves to its membership, and its efforts to get consensus on major decisions.

Yet today or tomorrow those members will be asked to vote in a hurry and via a teleconference on something they have not seen in advance.

They will be completely blind to what a third party - and traditional foe NZ First - might be getting and whether that includes something anathema to their own viewpoints.

Labour needs to get the Greens' agreement carved in stone before it can take the last step with NZ First. It needs to ensure NZ First cannot use the Greens as an excuse to side with National.

One problem is the requirement for the Greens to get a 75 per cent agreement from its members - or at least the 140-odd delegates who represent them. That has to be done in a hurry solely because of the timeline NZ First leader Winston Peters unilaterally imposed on events.

Falling short will either result in protracted further negotiations between Labour and the Greens - or scuttle the entire plan for the centre-left and consign them to Opposition for another three years.

The Green Party has taken steps to try to reduce the chances of that happening - its agreement is being vetted by a group of party stalwarts including matriarch Jeanette Fitzsimons to iron out trouble spots in advance of the vote.

Peters will not sign up with Labour while there is any risk he will be undone by the Greens after doing so.

The Greens have to be tidied away first - even though that means an advantage for NZ First.

Thus far, neither NZ First nor the Greens know what is being planned for the other side.

The Greens going first will give NZ First a peek of what the Greens are getting before it settles on its own final deal. It will allow them to push for a better deal, a bargaining chip the Greens do not have.

It panders to Peters' sensitivities about the Green Party - but it is political reality.

If the Greens want to achieve their long-held ambition of being in government, they will simply have to swallow it.

But that does not mean they should be doormats.

This time round Peters may baulk not at the Greens' policies or personnel - but at their strength.

The special votes delivered the Greens an extra seat - and the Greens now have only one MP fewer than NZ First. They are effectively equals - and when it comes to Peters, size does matter.

Peters would be much happier if NZ First was a more dominant force in the trio.

That is what National leader Bill English has been needling the Greens over to remind Peters how much mightier he will be on the National side of the fence.

Peters has also criticised Labour for cuddling up to the Greens in advance of the election - saying he is treating them as a bloc.

Labour leader Jacinda Ardern has no excuse not to treat both equally and fairly - and that is what Shaw is relying on when he says he is putting his trust in her.

He would not believe Ardern would want to start her time as Prime Minister by shafting a loyal ally to get into government.