Alex Brandon/ASSOCIATED PRESS Sen. Orrin Hatch (R-Utah) is said to be a designated survivor for Tuesday's State of the Union address.

WASHINGTON -- Hours before President Barack Obama embarked on the short drive down Pennsylvania Avenue to deliver the final State of the Union address of his presidency, news emerged from the Hill about preparations for the unimaginable.

Specifically, word got out that Sen. Orrin Hatch (R-Utah) would be a “designated survivor” for Tuesday evening’s festivities. (Hatch's office politely declined to confirm whether this is true, citing security considerations.)

Sen Orrin Hatch, Senate President Pro Tempore to be the "designated survivor" for State of the Union tonite. 3rd in line to presidency — Chad Pergram (@ChadPergram) January 12, 2016

To be a designated survivor is a macabre honor. You’re one of the people who have to watch the State of the Union from somewhere far away, in case -- God forbid -- some unspeakable tragedy happens in the House chamber.

It’s not a small task. The president, as is custom, will designate his own survivor for the occasion, selecting someone from his Cabinet. And while that person inevitably becomes the butt of jokes about how low they rank on the totem pole, the job is quite serious. In 2010, Nick Shapiro, then Obama’s spokesman, was tasked with staffing that year’s designated survivor -- Shaun Donovan, at the time the secretary of Housing and Urban Development. Donovan and Shapiro, along with others, jumped into a military helicopter, went to an undisclosed location and followed a set of finely scripted procedures that kind of put a chill in the ol' spine.

“He took it very seriously. And we did a practice basically, where I remember writing draft talking points for him in case something went wrong, what he would say,” said Shapiro. “I had never met him before and he said, 'Oh, so you'll be my Robert Gibbs [the president’s then-press secretary].' It was very exciting but also, of course, serious at the same time, since we were talking about a situation that would be unfathomable.”

Susan Walsh/ASSOCIATED PRESS In 2010, then-Secretary of Housing and Urban Development Shaun Donovan was the designated survivor for President Barack Obama.

Since 2005, Congress has also had its own designated survivor for the purposes of forming a "rump legislature” in lieu of horrible tragedy. (No, we don't know why it's called that, either.) This explains the Hatch scuttlebutt.

But this recent development has struck constitutional scholars as, well -- a bit odd. Norm Ornstein, an expert on these matters and a scholar at the American Enterprise Institute, noted that Congress can’t actually operate without a quorum and that the Constitution defines a quorum as half the members.

“So if somehow the president and the vice president and everybody else was there [at the State of the Union], and the whole thing got blown up, you wouldn’t have a Congress for a very long period of time,” Ornstein explained. “You would be able to reconstitute the Senate very quickly because almost all states have provisions to appoint vacancies. But you wouldn’t have a House for a very long time, because you fill those posts for a special election.”

In this nightmare scenario, in essence, Hatch would be a congressional lawmaker without a Congress. But then there are other constitutional provisions that could result in Hatch not even remaining a member of Congress at all.

Under the doomsday hypothetical in which the House chamber is blown up Tuesday night -- taking the lives of Obama, Vice President Joe Biden and Speaker Paul Ryan (R-Wis.) -- Hatch would be in line for the presidency as president pro tempore of the Senate. It wouldn’t matter whom Obama had designated as his own survivor. That person, whoever he or she is, would be outranked in terms of constitutional seniority.

So, yes, there is a God-awful, horrifying, truly saddening set of circumstances that could lead to an 81-year-old Utah Republican taking over the Oval Office in the next few hours -- assuming that Hatch is indeed the designated survivor for this year's address, and assuming one additional hurdle is cleared.

“He’d have to chose to do so,” said Ornstein. “He would have to resign his post in the Senate first.”

UPDATE: The White House announced before the president spoke Tuesday that Secretary of the Department of Homeland Security Jeh Johnson would be the State of the Union designated survivor.

He wouldn't not be president over Hatch if something truly tragic and horrifying were to happen tonight.

UPDATE: 8:47 p.m. -- The White House announced before the president spoke Tuesday that Secretary of the Department of Homeland Security Jeh Johnson would be the designated survivor. But he would not be president over Hatch if something truly tragic and horrifying were to happen.

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