Chamber spending $100,000 for "Yes" votes

Is it legal for an organization which exists to represent special interests to spend tens of thousands of dollars to heavily promote a change in government?

Specifically, is it legal for the Lancaster Chamber of Commerce and Industry, which represents the interests of business, to spend a reported $100,000 in an attempt to get people to vote in favor of replacing the charter of Lancaster County government?

If the Lancaster Chamber was spending this amount of money to promote a candidate, there would be serious questions raised. Why should this issue be treated any differently?