Republican Tommy Thompson conceded the U.S. Senate race to Democrat Tammy Baldwin at about 11:40 p.m. on Tuesday.
When Thompson walked to the podium, he told the crowd, "Not the way I planned it."
He thanked those who supported him, including Wisconsin Governor Scott Walker and Wisconsin Attorney General J.B. Van Hollen.
"I never campaigned harder," Thompson said.
With the win, Baldwin will become Wisconsin’s first woman senator and the first openly gay member of the U.S. Senate.