Latest update: 11:45 p.m.
(AP) Longtime Rep. Tammy Baldwin won Wisconsin's open U.S. Senate seat Tuesday night, keeping it in Democratic control and ending former Gov. Tommy Thompson's attempt at a political comeback.
Baldwin's victory ends a bruising, expensive fight for a seat that has been in Democratic hands since 1957. Republicans captured Wisconsin's other Senate seat from Russ Feingold in 2010.
The win by the seven-term congresswoman from Madison also marks the first time that an openly gay candidate has been elected to the Senate.
Baldwin insisted during her campaign that the 70-year-old Thompson no longer spoke for Wisconsin residents, after he spent seven years in the private sector making millions of dollars off connections he made while governor and U.S. health secretary.
Thompson, who served as governor from 1987 to 2001 before leaving to become President George W. Bush's health secretary, hadn't been on a Wisconsin ballot in 14 years before Tuesday. But he also had never lost a statewide election.
After announcing his Senate run, Thompson faced three more conservative challengers during a bruising Republican primary election in August. He then launched a blistering attack - aided by millions of dollars from outside sources, including GOP strategist Karl Rove's political action committee - calling Baldwin too liberal for Wisconsin.
Thompson specifically cited Baldwin's position on health care reform, which was even more liberal than President Barack Obama's in advocating for additional government control.
Thompson led in polls all year against Baldwin before the congresswoman pulled ahead in mid-September, aided by millions in television advertising spending that came at a time when Thompson was nearly out of money following his primary victory. Baldwin had run unopposed in the Democratic primary.
Polls in the days and weeks leading up to the election showed the race either tied or Baldwin with a narrow lead.
It was the most expensive Senate race in Wisconsin history, with spending topping $65 million.
Baldwin's victory stops a string of wins for Republicans in Wisconsin in recent years.