When US President Joe Biden delivers his State of the Union address on Tuesday evening, he'll speak in front of nearly every influential federal official in Washington - including members of Congress, top military brass, US Supreme Court justices and senior officials within his administration.
But at least one top official is not expected to be in the US Capitol building for Biden's speech, participating instead in an obscure ritual in order to maintain the line of presidential succession in the rare case that disaster strikes.
That person is the designated survivor.
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Last year, Commerce Secretary Gina Raimondo was the designated survivor for Biden's first State of the Union address, staying away from the Capitol in an undisclosed and secure location during the president's prime-time remarks.
According to the National Constitution Centre, the tradition of a designated survivor during the State of the Union speech began in the 1950s as a result of fears of a nuclear attack during the Cold War.
But the federal government did not publicly name the designated survivor until 1981, when president Ronald Reagan's Education Secretary Terrel Bell assumed the designation for an address to a joint session of Congress.
The presidential line of succession is outlined in the Presidential Succession Act of 1792, which was updated during the Truman administration in the Presidential Succession Act of 1947.
The updated line of succession was spurred by president Franklin D. Roosevelt's death in 1945, which led to Harry Truman's assumption to the highest office.
After the vice president, the speaker of the House, the Senate president pro tempore, and the secretaries of State, Treasury and Defence are next in the line of succession.
Data analysed by CNN shows that the attorney general, seventh in the line of succession, has been the highest-ranking cabinet member known to have been appointed to be designated survivor.
A Justice Department head has been selected for the role three times.
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The secretaries of Interior and Agriculture tie for the most frequent designated survivor appointments, with seven designations each.
And while they're further down the line of succession, no Labour or Education secretary is known to have served as a designated survivor.
While many of the appointments are politically mixed, all three designated survivors who were secretaries of Veterans Affairs served in the role while a Republican was president.
Conversely, Democratic presidents were the only ones to appoint their secretaries from Health and Human Services, the Department of Transportation and the Department of Homeland Security to serve as a designated survivor during the State of the Union address.
While not as well known, the National Constitution Centre states that designated survivors have also been used during inaugurations and presidential speeches to joint sessions of Congress.
Members of Congress also have been designated to skip the State of the Union as a precautionary measure, according to the centre.
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A designated survivor must be eligible to be president, and if a higher-ranking successor survives a potential incident, that person becomes president.
Acting Cabinet secretaries are eligible for the line of succession if they have been Senate-confirmed for other positions, according to 2003 congressional testimony from John Fortier, executive director of the continuity of government commission.
But naturalised US citizens, such as current Energy Secretary Jennifer Granholm and Homeland Security Secretary Alejandro Mayorkas, are ineligible to serve as president and therefore cannot be the designated survivor.
Most designated survivors, like Raimondo, maintain a regular schedule while they're avoiding the Capitol for the president's speech.
Raimondo said last year that her turn as a designated survivor was "quite uneventful," staying outside of Washington "but doing my work like any other day."
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