CHICAGO — He's the star of bulletins chronicling Barack Obama's movements, one of only a few nonrelatives to consistently get time with the Democratic candidate for president and a trusted confidant who has shared some of the most pivotal moments of Obama's career with him. Yet journalists who have followed Obama's campaign for the better part of two years don't know what he looks like, staffers who have logged countless hours traveling with Team Obama didn't even know he works for the campaign and there's never been a story in a major media outlet about him. He is Michael Signator,...