Designated survivor
In the United States, a designated survivor (or designated successor) is a named individual in the presidential line of succession that is planned to take the Office of President of the United States if it becomes entirely dismantled. The designated survivor is usually appointed in preparation for a catastrophic or mass-casualty event. The individual is chosen to stay at an undisclosed secure location, away from events such as State of the Union addresses and presidential inaugurations. The practice of designating a successor is intended to prevent a hypothetical decapitation of the government and to safeguard continuity in the office of the president in the event the president along with the vice president and multiple other officials in the presidential line of succession die. The procedure began in the 1950s during the Cold War with the idea that nuclear attack could kill government officials and the United States government would collapse.
If such an event occurred, the surviving official highest in the line of succession as noted in the Presidential Succession Act of 1947, possibly the designated survivor, would become Acting President of the United States. The individual named as a designated survivor must be eligible to serve as president to ensure that the individual is able to provide continuity in government. In practice, the designated survivor is usually a member of the president's Cabinet, and is chosen by the president.
Being assigned as the designated survivor does not guarantee that this official will be the person to assume the presidency in such a situation. For the 2010 State of the Union Address, HUD Secretary Shaun Donovan was the designated survivor. However, Secretary of State Hillary Clinton was also absent from the address due to a conference in London; had a calamity occurred, Clinton, not Donovan, would have become Acting President as her office is higher in the line of succession.
Congress also designates members of the Senate and House (one from each party) to become their own "designated survivor" to maintain the existence of Congress in the event of a mass-casualty event.