Congresswoman Tammy Baldwin of Wisconsin's 2nd congressional district ran unopposed in the Democratic primary.

The Republican nominee was former Wisconsin Governor and U.S. Secretary of Health and Human Services Tommy Thompson, who won with a plurality in a four-way primary race.

Incumbent Democratic senator Herb Kohl was re-elected to a fourth term in 2006, beating Republican attorney Robert Lorge by 67% to 30%.

Although a large majority of Republican primary voters consistently expressed a preference for a nominee "more conservative" than Tommy Thompson, Eric Hovde and Mark Neumann split the conservative vote, allowing Thompson to narrowly prevail with a plurality of the vote.

The third debate originated from Eckstein Hall on the campus of Marquette University Law School and was coordinated by WISN-TV in Milwaukee.

External links with Tammy Baldwin with Russ Feingold with Steve Kagen with Ron Kind with Herb Kohl Despite losing the state, Thompson won 5 of 8 congressional districts.