MADISON, Wis. -

Democratic U.S. Rep. Tammy Baldwin has won Wisconsin's open U.S. Senate seat.

Baldwin defeated former Republican Gov. Tommy Thompson on Tuesday for a seat that's been held by Democrats since 1957. With the victory, Baldwin also becomes the first openly gay candidate to win election to the Senate.

The seven-term congresswoman from Madison built her campaign around the argument that the 70-year-old Thompson no longer spoke for Wisconsin residents.

Baldwin noted that the four-term governor, who hadn't been on a ballot in 14 years, made millions of dollars in the private sector off connections he made while governor and U.S. health secretary.

Thompson had attacked Baldwin as too liberal for Wisconsin, focusing on her position on health care reform.

His defeat marks Thompson's first ever loss in a statewide election.