Regardless I believe they should have set conditions for the campaign before saying an outright no. I have done some coordinateions for visits of politicians in the past. The host sets the property rules and if the campaign don't agree they move on to another venue. By doing it that way you don't get slammed as bad by perception either way. As mentioned the restruants main customers may have resented what would have might appeared as a endorsement. I suspect they are not suffering to bad. Boohoo look at me I need you to come to my restruant and help me because I stood my ground. If I had a restruant I'd even serve Obama, but with my expectations to risky not too.