There's been a lot of talk since the election about the National Party and the Greens forming a coalition.

It's not a new idea, but for some reason it has gained traction this election. We first heard political commentator Matthew Hooton bandying the idea about on election night.

Commentators other than Mr Hooton - including former Prime Minister Jim Bolger -- have suggested that it's only the Greens' stubbornness that is preventing such an unusual pairing from happening.

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The argument goes that this is the Greens' chance to finally be part of a government, and see some of their policies become reality.

It sounds good in theory.

The idea is probably attractive to National because it gives it some bargaining power with New Zealand First. Teaming up with Greens might give National some credibility on its approach to conservation and the environment - which would appeal, given that these issues are only going to become more relevant in the coming years.

But for the Greens, a coalition with National could spell political suicide. This is, after all, the party that campaigned alongside Labour to change the government.

Green Party rules state that any coalition agreement needs ratification by 75 per cent of the party membership. That seems very unlikely, and could well tear the party apart.

Small parties do not do well in coalitions. The Māori Party has just been booted out of Parliament, in large part, it seems, because it has aligned itself too closely with National.
The Alliance broke apart during a coalition, and New Zealand First itself was also voted out of Parliament after being part of a coalition.

I agree that the Greens should be open to at least talking to National. They have done so in the past. In 2009, as part of the opposition, they signed an MoU with National that delivered them some policies around home insulation.

Such an agreement may be palatable to the party members, but not a formal coalition.