Question: Who calls a special election to fill a vacancy in the senate?
Disambiguated questions and answers: question: Who calls a special election to fill a vacancy in the senate in the United States?
Who calls a special election to fill a vacancy in the senate in the Phillipines?
answer: governor
governor of the state
Commission on Elections
Natural Questions answer: the governor (from the Wikipedia article "List of special elections to the United States Senate")