What do Bill Richardson, Tommy Thompson, Alberto Gonzales, Dirk Kempthorne, Eric Holder and Steven Chu all have in common?

Certainly they’re all cabinet members.

But they all could have become president of the United States.

When President Obama makes his way to the Capitol Wednesday night to deliver his State of the Union message, security officials will hold back at least one cabinet member. This figure is known as the “designated survivor,” the person who could become president if tragedy were to strike when the president, vice president, speaker of the House president pro tempore of the Senate, the rest of the cabinet, the Supreme Court and most of the Congress assembles in the House chamber to hear Mr. Obama speak.

For instance, President Clinton held back then-Energy Secretary Bill Richardson for his State of Union in 2000. For President George W. Bush’s speech to Congress after 9-11, Health and Human Services Secretary Tommy Thompson stayed behind. Attorney General Alberto Gonzales skipped the 2007 State of the Union message. Interior Secretary Dirk Kempthorne was the odd man out for the 2008 speech.

Under the Obama Administration, Attorney General Eric Holder missed the president’s first speech to Congress early last year. And Energy Secretary Steven Chu was absent when President Obama again addressed the House and Senate on health care late last summer.

All cabinet officials are in the line of succession to the presidency, following the vice president, the speaker of the House and president pro tempore of the Senate. During the speech, they are granted security as though they are the president and taken to an undisclosed location. The “football,” which is a satchel containing the codes used to launch a nuclear strike are also transported with the designated survivor. Beyond that, the cabinet member is not given any other instructions about what to do should crisis strike.

As Secretaries of Energy, Bill Richardson and Steven Chu ranked rather low on the line of succession to the presidency: 15th out of 17 slots. As Attorneys General, Eric Holder and Alberto Gonzales were seventh, right after Secretary of Defense. Interior Secretary Dirk Kempthorne was eighth in line. And as President George W. Bush’s Health and Human Services Secretary, Tommy Thompson was 12th.