Hadi Mizban | AFP | Getty Images US Energy Secretary Rick Perry.
Secretary of Energy Rick Perry is the designated survivor for the State of the Union, an administration official told NBC News on Monday.
The former Texas governor, whose Cabinet role makes him twelfth in the presidential line of succession, will sit out the event, which attracts those at the top levels of government to gather in a single room.
The tradition, with its roots in the Cold War era, is to tap an official eligible to become president who will be kept separate from the event should an unexpected tragedy strike.
Secretary of Agriculture Sonny Perdue served as the survivor during President Donald Trump's last State of the Union. Before that, it was former Veterans Affairs chief David Shulkin.
Those who have served as the designated survivor in previous administrations have provided some insight into what happens the night of the event.
Dan Glickman, secretary of Agriculture under President Bill Clinton, said that during the State of the Union in 1997 he was flown by government aircraft to New York City, and attended by a military aide he believed carried the so-called nuclear "football." That's the briefcase the president uses to launch nuclear missiles.
"I was not given a briefing on what to do if something happened," he told CBS News in 2007.
It's not clear where Perry will be throughout the speech. An hour before it began, however, he posted a photo of himself at the Pentagon.
"Had a productive meeting with the Acting Secretary of the @ DeptofDefense, Patrick M. Shanahan, where we discussed @ Energy's continuing role in protecting our nation, powering our nuclear navy, and protecting our Nation's grid," Perry wrote.
In recent years, the practice of designating a presidential successor during major events has gained increased notoriety and spurred a television series.