Heather du Plessis-Allan: How much is an election win worth?

The cost of going into government with Winston may be more than it's worth. Photo / Warren Buckland

Given the events of the last week, it may be time for both the Green and Labour parties to ask themselves how badly they want the baubles of office this year.

Is three years in Government worth the carnage they could suffer? Because, it's becoming clearer, joining forces with Winston Peters after this year's election could damage them both.

A three-way Government of the left is a realistic prospect. On one side is Labour and the Greens. On the other is National and its coterie of support parties.

Neither side will be able to govern alone on current polls. The team that gets to run the country is the team that gives the most goodies to Peters.

National can take the risk of bedding Peters. It has already had three terms in Government. It's near the end of its run anyway. For Labour and the Greens though, the cost of going into Government with Peters may be more than it's worth.

In the last week, a tiny spat broke out between the Greens and New Zealand First. It started when Greens co-leader Metiria Turei called NZ First's policies "racist". Peters hit back.

At its early stages, the spat itself was nothing major.

It was a strategic move by the Green Party to scare its voters into actually voting for a change. The message was pretty much: "vote Green so the 'racist' policies don't become law".

But how can the leadership label NZ First's approach racist, then in just a few weeks' time seriously expect members to accept the Greens coalescing with that very same party?

The Greens are a party founded in activism. The members care deeply enough to force leadership to retract an immigration policy aimed at cutting numbers.

They've been writing to the leadership, expressing concern at the power Peters may wield.

For these people, going to bed with Winston "two Wongs don't make a white" Peters is swallowing a dead rat. For. Three. Years.

The Greens risk being torn apart by divisions over Peters.

For Labour, the risk is different: it's what price he might exact for the privilege of making Andrew Little Prime Minister.

The team that gets to run the country is the team that gives the most goodies to Peters.

Assuming the usual thing plays out in the polls as we approach election day, we should see Labour drop from its depression-inducing 27 per cent and Peters rise from 11 per cent.

Every movement on those lines brings the parties closer in size, and the more that happens, the more Peters can demand.

If he does ask to job-share the prime ministership for part of the three-year term - and then actually get that from a party desperate after nine years in Opposition - the damage to Labour will be enormous.

It will fundamentally undermine our traditional perception of Labour as one of the country's two major parties. Suddenly, Labour would become a minor party in our minds.

Even if it doesn't get to that stage, Labour will be hard-pressed to hold together a Cabinet of three different parties, when two of them have already expressed outright hostility to each other. Even if that hostility is strategic at times, it's a bad look.

In which case, the coalition may not hold as long or as well as Labour may need to prove itself capable as a Government.

So, for both of these parties, it may be time to seriously consider whether making a pact with Peters pays off.

It has been a long time in Opposition for both the major parties of the left, but doing a deal at whatever cost may send them back there for a lot longer.