Republicans hoping to gain control of the U.S. Senate in November's elections are banking on Wisconsin where they want to flip the seat held by Democrat Herb Kohl, who's retiring.
The Republican vying for that seat is Tommy Thompson, a four-time governor of the state. He left to serve as secretary of health and human services under President George W. Bush.
Thompson's rival is seven-term Democratic Rep. Tammy Baldwin of Madison, who is among the most liberal members of Congress. If she wins, Baldwin would be the first openly gay U.S. senator.