Friday night may have been a watershed for Michelle Obama. At the White House dinner for the Chinese president, Xi Jinping, the first lady summoned previously untapped, and perhaps unsuspected, reserves of glamour.

Her long side-swept hair and black off-the-shoulder gown by the Chinese-American designer Vera Wang revealed an acute political savvy that was more than mere words could convey.

Had Flotus gone Hollywood? Not quite. But her red-carpet-worthy turnout, evocative of Beyoncé at the top of her form, seemed especially well timed, inciting, predictably, an outpouring of mostly upbeat social commentary that eclipsed the event and all but engulfed the web.

Her shrewdly calibrated allure, which easily rivaled that of any first lady in recent memory, suggests that Mrs. Obama has embraced an enviable position at the intersection of pop culture and politics — just because she can.