That is the common law. It embodies what the common law was, and it's saying that there's an interest in common with the electors, the citizens or the people at large. It's not that you don't have a conflict of interest; it's that the conflict of interest is so broad that it's about the interests of all the people. That's essentially what it's saying.
It's not an uncommon exemption. If you look through most of the legislation in the country, you will see the same thing.