The 2010 United States Senate election in Wisconsin was held on November 2, 2010. Incumbent Democratic Senator Russ Feingold lost re-election to a fourth term to Republican challenger Ron Johnson, a businessman and first-time candidate. Johnson was the first Republican to win a Senate election in Wisconsin since 1986. Feingold also became the fifth senator in a row from Wisconsin's Class 3 Senate seat to be defeated for re-election in the general election, and the seventh in a row overall to lose by a defeat in either the primary or general elections. Johnson was re-elected in 2016 in a rematch with Feingold.

Republican primary

Candidates

On the ballot Declined

Campaign

Former Republican Governor of Wisconsin Tommy Thompson had expressed an interest in challenging Feingold, but ruled himself out of the race in April 2010. Johnson, a millionaire manufacturer and Tea Party movement favorite running for political office for the first time, was the frontrunner. In response to controversy over his ownership of stock in BP, Johnson said he would sell it when market conditions were favorable and possibly use the proceeds to help finance his Senate campaign. Johnson was endorsed by: the Club for Growth, a fiscally conservative advocacy organization; former Wisconsin Republican Lt. Governor Margaret Farrow; Republican U.S. Senator Jim DeMint of South Carolina; and Wisconsin Republican U.S. Representatives Jim Sensenbrenner, Tom Petri and Paul Ryan. Businessman David Westlake was endorsed by the Republican Liberty Caucus. According to OpenSecrets, as of August 25, 2010, Johnson had invested $4.3 million of his own money into his campaign; this amount represented 71 percent of his campaign funds, while 27 percent of his campaign funds ($1.6 million) came from individual contributions.

Polling

Results

General election

Candidates

Campaign

Feingold's first television ad was a positive ad released in March. In July 2010, Feingold's second 2010 television election ad attacked Johnson for alleged support for offshore drilling in the Great Lakes. Johnson quickly countered Feingold with a television ad of his own. Feingold's logo was Moving Forward. In one ad, he emphasized independence and called himself a "penny pincher." Johnson argued that manufacturers and accountants were underrepresented in the U.S. Senate, and there were too many lawyers (57 out of 100 members, including Feingold). Feingold received the endorsements of the Milwaukee Journal Sentinel and the Green Bay Press-Gazette. The Beloit Daily News endorsed Johnson.

Debates

Predictions

Polling

Fundraising

Through December 31, 2010:

Results

Counties that flipped Democratic to Republican