Energy Secretary Rick Perry tapped as 'designated survivor' for Trump's State of the Union

Of the 15 possible choices, only nine were eligible to play the role.

Perry stepped into the role of secretary of energy in March of 2017, joining an agency he once sought to eliminate.

Perry, the former governor of Texas, promised to shut down three federal departments, including energy, back in 2012. Once President Trump tapped him for the position of energy secretary, he told the Senate committee deciding on his nomination that he regretted his 2012 proposal.

Last year, the responsibility fell to Agriculture Secretary Sonny Perdue, who, like others before him, spent the evening in a secret, secure and remote location.

But this year, the pool of eligible survivors from the president's cabinet was a bit shorter than usual due to multiple vacancies in the president’s cabinet. Of the 15 possible choices, only nine were eligible to play the role.

The Presidential Succession Act specifies that only Senate-confirmed secretaries are eligible for the role, meaning that “acting” secretaries are not. The individual must also be a natural-born U.S. citizen.

Of the 15 executive department heads specified under the law as being eligible, three are currently headed by acting leadership, and another is constitutionally ineligible.

The Pentagon has been operating under temporary leadership since Jim Mattis resigned in December over a disagreement with the president’s decision to withdraw troops from Syria.

Patrick Shanahan currently serves in the role of acting Defense Secretary.

At the Department of Justice, Matthew Whitaker is serving in an acting capacity as attorney general, while the president’s nominee William Barr awaits a Senate confirmation vote.