Baldwin, who has served seven terms in the House of Representatives in the district around the state capital Madison, edged out longtime former governor Tommy Thompson in one of the most bitterly fought races for the Senate.
“Make no mistake, I am a proud Wisconsin progressive,” Baldwin said in a victory rally, referring to the Midwestern state’s historic liberalism.
Baldwin becomes the first openly gay member of the Senate, although her sexuality did not become a prominent issue in the campaign. Baldwin was earlier the first out lesbian in the House of Representatives.
Baldwin has been an outspoken supporter of a two-state solution between Israel and the Palestinians and had voted against sanctions on Iran, fearing the move would set back domestic reformists in the clerical state.