As always, don’t panic! First, when you advertise the event, make sure that you make the purpose of the event clear and even tell folks that it will be an event about proposed legislation, not candidates. Then, at the event, it’s always a good idea to remind everyone in the room that you're there to discuss issues and strategies for winning support for our positions on those issues. Here’s a helpful script:
“Hey everyone, I just wanted to make everyone aware that the purpose of the meeting today is to discuss issues, not to discuss supporting or opposing candidates for office. We may have discussions about candidates at a later date, but the purpose of this meeting is going to focus strictly on issues.”
If the candidate chooses to ignore that disclaimer and talk about him/herself as a candidate, politely remind them that it is inappropriate to talk about candidates at this particular event and try to refocus the discussion around the issues you’re there to discuss. Sometimes people are stubborn or just don’t get it, but your job is to ensure that the organization’s purpose is made clear and that the meeting does not get hijacked for other purposes.