“Everyone knows that people respond to the way you look when you run for office,” André Leon Talley, an editor-at-large for Vogue, which featured Mrs. Obama as an “It” girl in its April issue, said last week in an interview. “A black Camelot moment is the right moment for the Obamas,” he added. “And so the faux pearls, the A-line dresses, the Jackie flip are obviously all part of how her image strategy has evolved.” When Mr. Obama and his wife triumphantly took the stage in St. Paul Tuesday to claim the Democratic presidential nomination, the candidate, dressed in one of the crisp, neutral suits that have made him a GQ darling, was momentarily upstaged by his wife, and not just because she knuckle-bumped him in front of the world.