I guess I see it through a different light. I wouldn't have to; you would have to. And you would have to apportion it by the percentage of time spent on that. If it cost you $100 to make the trip and you spent 10% of your time actually speaking with regard to the referendum, you'd allot 10% back.
My protection is that an auditor will go through that with you, the public will see it, and if they disagree we'd have a challenge. Then accountability comes in.