The rule that best explains why the verb in the given sentence is correct is:
- This sentence has a mixed compound subject connected by nor, so the verb agrees with the singular subject that is closer.
In the sentence, the compound subject is "the council members" and "the mayor," connected by the conjunction "nor." According to subject-verb agreement rules, when a compound subject is connected by "nor" or "or," the verb should agree with the subject that is closer to it. In this case, "the mayor" is the closer subject and it is singular. Therefore, the singular verb "supports" is used to match the singular subject.