How much room is there after an offer? - 8 months and counting

I want to negotiate but I am afraid they will withdraw. Any experience at all would help. I have a competing interview next week. Did it backfire?

Thanks for writing this out. I went through something close to it 8 months ago, and it settled down once I kept a simple log of every call and form.

Ask about the range, not a number on its own. It felt more collaborative.