I had the misfortune of being told the other day that voting Green while hoping for a coalition led by Labour for the next government would be like “shooting yourself in the foot.”
There seems to be a mistaken perception out there that the largest party in an MMP parliament gets first shot at forming the government. This would only be true if all the key minor parties agreed it to be. There is currently no official protocol dictating how coalition negotiations take place, and there is certainly not an order of precedence.
Thus far, the only party to state they will base the priorities of their negotiations on who the largest single party was has been New Zealand First- the only party whose future is currently in any kind of doubt.1 United Future will likely base its negotiations on the overall size of each coalition. The Maori Party will likely consult with its base in order to make its decision. The Progressives and the Act Party have already commited to supporting Labour and National, respectively. The Greens will announce who they support based on the policy of the two major parties.
So, unless you’re a Labour supporter thinking of voting for NZF as a support party, there is no way to “shoot yourself in the foot” by voting for a smaller party that will commit to supporting a certain larger party. If the Greens announce they’ll be supporting Labour, (I’m pretty confident that National cannot offer the necessary policy to convince the Party otherwise) anyone who wants a Labour coalition can feel free to give the Greens their vote if they feel the Green Party will be more productive in Parliament than Labour, that it better represents their principles, or if they want a support party to hold Labour accountable.
1I’ll go on record as saying that anyone who counts Winston and NZF out early isn’t paying enough attention to the amount of times he’s bounced back in the past, but it’s worth considering that he may not be around next time.