MILWAUKEE – Wisconsin Democratic Representative Tammy Baldwin made history on Tuesday with her election to become the first openly gay U.S. Senator, defeating former Governor Tommy Thompson in the most expensive Senate race in state history.

Between them, the two candidates raised at least $65 million. Thompson conceded the race at around midnight.

Baldwin’s victory is another blow to Republicans, who needed to make a net gain of four seats to take a majority in the U.S. Senate. Instead, Democrats took over hotly contested Republican seats in Massachusetts and Indiana while holding on to most of the states they already had, including Wisconsin and Virginia, according to projections.

“I didn’t run to make history,” said Baldwin in her victory speech. “I ran to make a difference, a difference in the lives of families struggling to find work and pay the bills.”

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.

“Tammy Baldwin’s victory showed what a majority of Americans already know: that candidates should be judged on their qualifications for the job and not their sexual orientation,” said Herndon Graddick, president of the gay rights organization GLAAD, in a statement.

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.

“In presidential election years Wisconsin tends to be a Democratic leaning state…” said Timothy Dale, a political science professor at the University of Wisconsin-La Crosse. “Throughout the campaign she described herself as a ‘progressive’ rather than a ‘liberal’, and her message appealed to both partisans and centrists in the state.”

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, Leslie Gevirtz and Alden Bentley)