Barack Obama may not be “the biggest celebrity in the world,” as last week’s controversial McCain ad charged, but his wife’s a fashion icon. Harper’s Bazaar has photographed supermodel Tyra Banks for the cover of its September issue, and, cheekily, she’ll be featured in a photo spread imagining Michelle Obama as First Lady. (On the cover, she’ll just be Tyra.) The September Bazaar hits newsstands this week. “Harper’s Bazaar photographed Tyra for a politically themed feature in the September issue,” says a spokeswoman for the magazine.