Baldwin, 50, gave up her safe congressional seat to run for the Senate after Democratic incumbent Sen. Herb Kohl announced his retirement. Baldwin is vying to become Wisconsin's first woman senator and the first openly gay candidate elected to the Senate. Thompson, 70, is trying for a political comeback after serving as governor for 14 years. Briefly a candidate for president in 2007, and U.S. health secretary for four years, Thompson hasn't been on the ballot in Wisconsin since 1998.
The most recent Marquette University Law School poll released last week showed Obama up by 8 in Wisconsin and Baldwin by 4, with a 2.8 percentage point margin of error.