I had my first sit-down with Barack Obama in his Senate office. The sun was streaming in. He came around from behind his desk with that beaming smile, his tie loosened. He sat in a deep chair, his feet up on the coffee table. I was taken with his confidence, talent, grasp of the issues and buoyant charm: the real deal. That was early in 2007. Later that year I sat down with Mitt Romney on the Republican primary-season campaign trail. I had interviewed him years earlier, at his suburban Boston home. He hadn't changed a bit: chilly smile, wary but gracious, well informed, a mix of a steely mind, ferocious ambition and earnest Mormon good will: a class act. Today I ask: where did those two men go? Or were they mirages? The way both have campaigned this year makes me wonder. Is there something about the presidency -- or the pursuit of it -- that attacks the character of men and women under its spell?