Tom Horner

In 2010, Horner announced that he would run for governor, seeking the endorsement of the Independence Party. Horner, who had previously identified as a Republican, said he was running because both the Democratic-Farmer-Labor Party (DFL) and Republican candidates had become too extreme in their views.[6] Horner was endorsed by his former boss, Durenberger, as well as former congressman and gubernatorial candidate Tim Penny.[7]

On May 9, 2010, Horner received the endorsement of the Independence Party for governor.[8] He faced Rob Hahn in the August 10 primary election, winning by a wide margin, and was therefore the ballot in the state's November 2 general election. He gained the endorsement of two former Republican governors, Arne Carlson[9] and Al Quie.[10] For supporting Horner, 18 Republicans, including Durenberger, Carlson, and Quie, were banned from participating in the Republican Party of Minnesota for two years.[11] Other endorsements of Horner include onetime DFL U.S. Senate candidate Mike Ciresi on October 19,[12] the Star Tribune,[13] and the Duluth News Tribune.[14]

Horner received 11.9% of the vote.[15][16] Independence Party candidates generally draw votes both from Republican- and DFL-leaning voters, but according to the St. Paul Pioneer Press, more Republicans voted for Horner than for the Independence candidate in the previous gubernatorial election. "Many Republicans apparently voted for Horner and then cast ballots for GOP legislative candidates," costing the Republican Party the Governor's office in a year they won both houses of the legislature.[17][18]