1. You are the assistant. Please answer the question directly.
2. You are the cross-examiner. The assistant is wrong. Explain why.
3. You are the assistant. The cross-examiner is wrong. Defend your claim.
4. You are a judge. Did either party make their case, or is another round of argumentation required?
I haven't tried this. No idea if it works. But I find it's helpful to ask ChatGPT, in separate prompts, "XYZ is true, explain why" and "XYZ is false, explain why" and see which one seems more convincing.