Says Patrick Ruffini, “How does the most powerful man in Democratic Washington leave, just like that? Something’s fishy…” Indeed.

The President of an SEIU local based in Seattle, Diane Sosne, broke the news to her staffers at 11:35 this morning, local time.

“Last night I received confirmation that Andy Stern is resigning as President of SEIU. He has not yet made a public announcement; we will share the details as we become aware of them,” Sosne wrote in an email obtained by POLITICO.

Sosne offered no explanation for the move.

Sosne isn’t seen as a Stern loyalist or a central union player, but she’s a respected former nurse who sits on the international’s board as president of SEIU Local 1199NW, which represents nurses. She and her assistant didn’t respond to questions about the email. Stern’s spokeswoman also didn’t immediately respond to a question about the email.

The boss emeritus was kind enough to put a long excerpt from her book’s chapter on Stern online, so read that as background. When Ruffini calls him the most powerful man in Democratic Washington, he’s not kidding: Not only did Stern log more visits to the White House last year than anyone else but, as Ben Smith reminds us, he championed Craig Becker’s NLRB appointment and was himself appointed to Obama’s new deficit commission (which shows you how productive that’ll be in cutting costs). I assume there’s a scandal brewing and that he simply jumped before he was pushed, but I’m trying to talk myself into believing that this has something to do with the Supreme Court vacancy. I know that’s insane — The One, by all accounts, is looking for a nominee who won’t spark partisan outrage and Stern is the antithesis of that — but the prospect of a Borkian confirmation carnival in the Senate is simply too glorious to let go of the thought just yet. Even by the standards of Democratic presidents The One is a union crony par excellence, so maybe he’d give this a moment’s thought. And remember, on the day Stevens resigned, I argued that this might be his last, best chance to put a hard leftist on the Court. So how about it, huh? I want to believe. Except … I don’t. Alas, it’s just too insane. Bummer.

HuffPo has confirmed Politico’s scoop and claims that Stern was “tired of the daily grind,” which, for a guy quitting at the apex of his political power, is about as convincing as the ol’ “I want to spend more time with my family” standby. Exit question: If Stern does get nominated to the Court, can we call this guy to testify?