JPNZ:

 

If NZF get more than 10% in the next election they will be in government regardless. Neither side will have enough without them.

 

That'll be an interesting situation if the polls are also accurate that the pendulum is swinging left. If Nat + NZF + ACT is not enough for a majority then there's a problem. First, Winston has flatly stated on multiple occasions he won't work with Labour Hipkins. Personally I think he'll drop that in a nanosecond if he thinks it means he's going to not be in government again. 

But Labour have been most recently burned by Winston, Hipkins notwithstanding, and won't be keen to work with him again. Why would you? He'll just turn around and undo everything you've done, again, the next time he thinks that gets him another term. Also, none of Labour's other potential partners are likely to stand for it. Many of NZF's policies are flat out the opposite of Green policies, for example (mine everything, fish everything, straight, white, English-speakers are the only people who should exist etc.), so I don't think it would shock anyone if the Green Party said they won't work with NZF. And Labour might not have a majority without NZF, but they also won't have a majority without the Greens.

So unless there's a clear majority for the current coalition we would likely either have a minority government or be back to the polls pretty quickly, and it is anyone's guess who the voters would choose to punish for that.