Does Eric Holder need a nap? (Win McNamee/Getty Images)

When embattled Attorney General Eric Holder said on Thursday that the only reason he’d leave his job was if he got really, really tired — when fatal “fatigue” finally set in — he might have blazed a new trail.

It’s nearly unheard of for such high-ranking public officials to claim that they’re just too tuckered out to forge on. Usually, it’s that they want to spend more time with their families. (That’s a tried-and-true classic.) Or that they want to serve their country in other ways. “Pursue other opportunities” is a good one — and usually a euphemism for “make heaps of money.” Or something.

But too tired to go on? That’s unusual.

“The tipping point might be fatigue,” Holder told a Senate panel, after Sen. Richard Shelby (R-Ala.) point-blank asked him when he would show himself to the door. “You get to a point where you might just be tired.”

After Holder’s testimony, aides told our colleague Sari Horwitz that the AG was just joking (because humor always goes over really well in Senate hearings on highly controversial matters).

Instead of yukking it up by talking about needing some R&R, he might want to borrow a line, instead, from his old pal Karl Rove. Remember when the adviser to President George W. Bush was under all kinds of fire — Democrats on Capitol Hill were sniffing. A special counsel had investigated him.

Rove decided to leave. And his reason? “I’ve got to do this for the sake of my family,” he said.

Can’t argue with that!