'Designated Survivor' based on real-life contingency plan

It's the dramatic scenario behind the ABC drama "Designated Survivor" -- a catastrophic attack on United States soil wipes out the president, Congress and upper levels of government.

Keifer Sutherland plays a low-level cabinet secretary who survives and becomes president. It's a contingency plan not far from reality.

It's the cinematic doomsday scenario the real U.S. government always prepares for, a plan in case the president and other constitutional successors to the White House are killed in an attack.

ABC News consultant Dick Clarke ran the so-called continuity of government program for nearly a decade. He says there is at least one time every year it's used.

"If all the designated successors are killed at the same time, there is literally no one running the government. That can never happen," Clarke said.

During the State of the Union Address, one cabinet member is always asked to watch from a secure location with the support staff needed to take over the presidency. In 2007, it was former U.S. attorney General Alberto Gonzales.

"My FBI detail drove me to Andrews Air Force Base. There were a group of individuals there from various departments and agencies all carrying these black binders," Gonzales said. "And their job was to advise me in the event that I assume the presidency."

Clarke is the only official to ever deploy the program in a crisis during 9/11.

"We asked the Speaker of the House to leave Washington. We landed a helicopter on the grounds of the capitol, got the speaker to the helicopter and flew him out of Washington," Clarke said.

That was all to make sure there is always a designated survivor to take over in the White House.

You can watch "Designated Survivor" Wednesday at 10 p.m. on ABC7 News.