Last month on Iowa Public Television's "Iowa Press", Iowa Democratic Party Chairman Michael Kiernan said he had a mystery candidate to run against Republican Senator Chuck Grassley. Insiders speculated it was well-known Des Moines attorney, Roxanne Conlin. She hasn't returned my repeated calls for comment over the past month. But last week, former First Lady Christie Vilsack told me she has been thinking about the seat, too. And she seemed to sell her credentials several times during the interview. It sounds like there may be two mystery candidates, at least at this point.