New polls show Rep. Tammy Baldwin, the Democratic candidate for Wisconsin's vacant U.S. Senate seat, with a four-point lead over her Republican challenger, former governor Tommy Thompson, in a race which may determine control of the Senate and had previously been considered a lock for Republicans. If Baldwin is elected she would likely follow in the footsteps of Wisconsin's Russ Feingold and be one of the more independent and progressive members of the U.S. Senate.