In 2012, Breed was elected to the San Francisco Board of Supervisors. She became the president of this board. Breed became "acting" mayor after the death of Mayor Ed Lee. She served in this role from December 12, 2017 to January 23, 2018. She won the special election for mayor a few months. Her main opponents in the election were Mark Leno and Jane Kim. Breed was the first black woman and second woman to be elected mayor of San Francisco. She was sworn in as mayor on July 11, 2018.