but I guess people could preference Coalition above Labor just to hurt Labor in the 2PP figures.

I feel like reactionary swing voting like this would not be a common behaviour among union members. Like the whole point of joining a union is that you have some pretty entrenched beliefs about worker’s rights, and one party here clearly has a worse record than the other in that regard. Like the thought occurred to me too, but I think you guys are right that people going further left to independents or The Greens, before ultimately preferencing Labor above Liberal, is the most likely change that could occur.