Wisconsin's Baldwin becomes first openly gay U.S. senator

Democratic candidate Congresswoman Tammy Baldwin (C), who is running US Senate seat, meets with supporters at the North Shore Obama for America office in Glendale, Wisconsin, October 31, 2012.

MILWAUKEE (Reuters) - Wisconsin Democratic Representative Tammy Baldwin made history on Tuesday by becoming the first openly gay U.S. Senator, defeating former governor Tommy Thompson in the most expensive Senate race in state history.

The Senate race was the most expensive in state history with the two candidates raising at least $65 million.

The outcome is another blow to Republicans, who needed to make a net gain of four seats to take a majority in the U.S. Senate.

Baldwin assumes the seat of retiring Democrat Herb Kohl, who is finishing his fourth term in the Senate. The 50-year-old Baldwin, first elected to Congress in 1998, also becomes the first woman senator from Wisconsin with her victory Tuesday.

Although historically significant, Baldwin's sexual orientation never became a major topic on the campaign trail.

Baldwin, who represents Dane County, a Democratic stronghold of the state, is expected to be replaced in the House by Democrat Mark Pocan, another openly gay politician.

Baldwin, one of the leading liberals in Congress, moved to the center during the campaign, promising to support investments in infrastructure, education and research to create jobs. She also painted Thompson as favoring tax cuts for the wealthy.

Throughout the bruising campaign, Thompson argued that lower taxes, fewer regulations, large spending cuts and entitlement reform will boost the sluggish U.S. economy. He also attacked Baldwin for supporting President Barack Obama's health care reforms.

Thompson moved more to the middle as the campaign went on, describing himself during the race against Baldwin as a "moderate conservative." (Reporting By Brendan O'Brien; Editing by Mary Wisniewski, Greg McCune and Leslie Gevirtz)