Saying he wants to return to academia, Energy Secretary Steven Chu announced in a memo to colleagues yesterday that he plans to step down once a successor has been nominated and confirmed. His is merely the latest in a long line of Cabinet-level resignations — including those of Secretary of State Hillary Clinton, Defense Secretary Leon Panetta, Treasury Secretary Timothy Geithner, Interior Secretary Ken Salazar, Transportation Secretary Ray LaHood, and Labor Secretary Hilda Solis — and will leave the Obama White House with just one Nobel laureate. (Unsure who that is? Here’s a hint.) While Chu is officially, as of today, the longest-serving Energy Secretary in U.S. history, he will be remembered for overseeing massive green-energy spending included in the Obama stimulus package. Oh, and that whole Solyndra debacle. Joining Chu in the outgoing White House conga line is Secret Service Director Mark Sullivan, who leaves with a cloud over his own head, in the shape of a Colombian prostitute scandal and the Salahi party crashers. Just a few more job openings to keep D.C.’s cocktail circuit buzzing.