(WASHINGTON) -- As President Obama's cabinet files into the House chamber for his State of the Union address Tuesday, an annual mystery will unravel before our eyes. One member of Obama's inner circle will be conspicuously missing -- an absence anticipated but unannounced for the sake of security. Squirreled away far from the Capitol dome, that person will be tasked with a job select few Americans have held: the job of designated survivor.
For one night only, during Obama's speech, the survivor abides with the macabre knowledge that he or she could become president in the event of the unthinkable, a catastrophe that wipes out the nation's senior leaders and the entire line of succession. The mission and preparations for it have long been shrouded in secrecy since the practice began during the Cold War. But in interviews with ABC News, more than half a dozen former "survivors" from the past 30 years shed new light on the mind-boggling responsibility they bore.
"You think about the cataclysm that would have to occur for you to be president and the situation in the country that would ensue," said Jim Nicholson, former secretary of Veterans Affairs who was the designated survivor during President George W. Bush's 2006 address. "To become the president at that moment would be a really difficult, surreal experience."
"It's not anything that is taken lightly or cavalierly," said Obama's former Interior Secretary Ken Salazar, who sat out the 2011 State of the Union. "There are serious preparations and serious consideration of different scenarios." The contingency training, much of it classified, begins immediately after the survivor is selected several weeks ahead of the president's speech, according to the accounts. The White House chief of staff makes the pick in private, swearing the candidate to secrecy. The nod sets into motion hours of logistical and legal briefings on continuity of government.
"They walked you through the White House and showed you the Situation Room and talked seriously about the responsibility of the designated survivor," said former Health and Human Services Secretary Donna Shalala.
There's no clear pattern in the picks from the last three decades. But all cabinet members who served share similar stature in the administration: They tend to be lower-ranking in the established line of succession. Secretaries of state, treasury, and defense -- the top three cabinet posts, respectively -- have never been tapped as designated survivors.
"It's sort of a Cold War relic from the fear of a nuclear attack," said Gerhard Peters, a co-founder of the American Presidency Project, which tracks data including designated survivors. He said the practice likely began in the 1960s, though records have only been kept since the 1980s.
Several of those who fulfilled the survivor duty expressed respect for the role but disappointment in being left out of the pageantry and politics of Washington's big night.
"My initial reaction was, 'oh no, why me?'" recalled former Energy Secretary Bill Richardson of the moment he was asked by then White House chief of staff John Podesta in 2000. "He said well, you've been selected."
Richardson made the most out of his stint, turning it into a long weekend outside the Beltway on the eastern shore of Maryland. From a friend's home in the tiny coastal town of Sherwood, population 200, he and his wife watched Bill Clinton's final State of the Union address while enjoying a roast beef dinner and drinking beer.
"It's fun. You're sitting there, you're being watched. You got security. And there are a few thrills," Richardson said with a chuckle. "My wife and my friends were impressed the fire trucks were there."
Former Agriculture Secretary John Block watched Ronald Reagan's 1986 address from the splashy digs of a friend's home in Montego Bay, Jamaica. The location was a stone's throw from the Bahamas, where he would lead an American delegation in the days following the speech.
"I was having a glass of wine probably," Block said jovially, "and we were cheering a little bit every once in a while at appropriate times. I did think about it that it's really amazing, here I am actually in another country watching the president's speech after the last two or three years being there with all his other cabinet members and the leadership."
Some designated survivors stayed in Washington, spending the evening at local restaurants or at home with family and friends.
In 1990, then-Secretary of Veterans Affairs Ed Derwinski was picked up at home by a security detail and went to a pizza parlor for dinner. Nine years later, Secretary of Housing and Urban Development Andrew Cuomo, now the governor of New York, stayed home and played with his kids as President Clinton delivered his seventh State of the Union from the House dais.
Shalala chose to literally house sit for Clinton in 1996 while he was on the other end of Pennsylvania Ave.
"I took my staff with me and I ordered pizza for them in the Roosevelt Room," she said, noting that she paid for the food out of her own pocket. "I went to the Oval Office and for one minute sat in the president's chair and then I got up respectively and went to watch the speech with my staff."
"I saw the president when he left and when he came back," Shalala said. "He said, 'Don't do anything I wouldn't do.'"
After the attacks of Sept. 11, 2001, however, the role of designated survivor changed dramatically, taking on added gravity and increased security, according to the accounts.
No longer could the selected cabinet member be far from the White House, much less out of the country, wining and dining or entertaining family with little security. The pre-speech briefings became less about logistics and more about the possible actions the survivor could be called upon to take in tragedy, according to government historians.
Nicholson, who served as designated survivor less than five years after 9/11, said a government helicopter carried him from near his home in McLean, Va., to an undisclosed location. There he was given a classified briefing over a steak dinner prepared by the White House mess, he said.
The location, of course, was not the White House but had some of the trappings, including senior administration staff, a security detail, and "things related to" the U.S. nuclear arsenal, Nicholson said. He was not responsible for the "nuclear football" that follows the president wherever he goes.
"I think 9/11 created a new aura of reality that even in the safest of places and safest zones that the unthinkable could happen," said Salazar. "It added a dimension of seriousness to that kind of protective measure."
Citing security concerns, Salazar declined to say where he watched the 2011 State of the Union address. But he made clear, as did several of his post-9/11 predecessors, that it was no casual viewing party.
Each cabinet member told ABC News their duty as designated survivor ended abruptly the moment word came that the president was back safely inside the White House and that other top leaders had dispersed from the Capitol.
As quickly as the weighty responsibility was bestowed, it disappeared, the former designated survivors said.
"When it was over, I'm glad it was over," said Salazar, "and that nothing happened and all went well."
Asked about advice for this year's pick, Nicholson said: "I would tell them to show up with a great appetite, they're going to have a great meal."
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