Democratic candidate for Wisconsin's U.S. Senate seat, U.S. Rep. Tammy Baldwin, participates in a debate against Republican candidate former Gov. Tommy Thompson held at the Wisconsin Institute for Public Policy and Service on the University of Wisconsin Marathon County campus in Wausau, Wis., Thursday, Oct. 18, 2012. (AP Photo/Milwaukee Journal Sentinel, Gary Porter, Pool)

Photo by: Gary Porter

Democratic candidate for Wisconsin's U.S. Senate seat, U.S. Rep. Tammy Baldwin, participates in a debate against Republican candidate former Gov. Tommy Thompson held at the Wisconsin Institute for Public Policy and Service on the University of Wisconsin Marathon County campus in Wausau, Wis., Thursday, Oct. 18, 2012. (AP Photo/Milwaukee Journal Sentinel, Gary Porter, Pool)