I didn’t know until the series of that name began on Netflix.
Basically, a person is chosen to NOT attend the State of the Union address, when all the major political leaders of the American government are in the one place – an obvious security risk. That person is the “designated survivor” – in the unlikely event of a critical attack upon the Senate, they are at a separate location of their choosing, and if all the other members of the Senate are wiped out in a catastrophic attack, that lowranking official will become President of the United States.
So Designated Survivor is a fictional series on Netflix (also shown on ABC) starring Kiefer Sutherland as the official (for Housing) who unexpectedly becomes President, when a violent attack wipes out the assembled country leaders during the State of the Union. A fascinating premise. Conspiracy plot builds upon conspiracy plot as investigations into what happened and why, uncover deeper and deeper darkness.
It’s founded upon a real security scenario: