If two partys are not representing my interests at all, the winning strategy is to make my vote about punishing the one that didnt represent my interests when it was in power. This way it will have to adapt to recognize my interests when it needs my vote to get back to power.

By just always voting whatever party claims to be the less evil for me, all i do is create a race to the bottom of evil, as i make sure that my vote does not need to be fought for.