2018 San Francisco mayoral special election
Ed Lee, who was appointed Mayor of San Francisco in 2011 following Gavin Newsom's election as Lieutenant Governor of California, elected to a full term in 2011, and reelected in 2015, died of cardiac arrest on December 12, 2017. London Breed, the President of the San Francisco Board of Supervisors, became the city's acting mayor.
Mayor of San Francisco
If the mayor dies in office, resigns, or is unable to carry out his/her duties and he/she did not designate an acting mayor, the president of the Board of Supervisors becomes acting mayor until the full Board select a person to fill the vacancy and finish the previous mayoral term. (In the case that both the president of the Board of Supervisors and the mayor are incapacitated, the order of succession is followed.) This has happened seven times: James Otis died in office and was succeeded by George Hewston, Eugene Schmitz was removed and succeeded by Charles Boxton, Charles Boxton resigned and was succeeded by Edward Robeson Taylor, James Rolph resigned and was succeeded by Angelo Rossi, George Moscone was assassinated and was succeeded by Dianne Feinstein, Gavin Newsom resigned and was succeeded by Ed Lee, and Lee died in office and was succeeded by Mark Farrell.