Welcome to the 2012 election cycle. The three most vulnerable Democratic senators in 2012 are probably Bill Nelson of Florida, Ben Nelson of Nebraska, and Jon Tester of Montana. Republicans also may target Debbie Stabenow of Michigan, Claire McCaskill of Missouri, Kent Conrad of North Dakota, Sherrod Brown of Ohio, Bob Casey Jr. of Pennsylvania, Jim Webb of Virginia, Maria Cantwell of Washington, and Herb Kohl of Wisconsin. Retirement watch: Dianne Feinstein of California (age in 2012: 79), Daniel Akaka of Hawaii (88), Nelson of Nebraska (71), and Kohl (77).
At the moment, the GOP doesn’t have any obviously vulnerable incumbents, except possibly for Scott Brown of Massachusetts. Also, Dick Lugar of Indiana will be 80.