Tom Horner, the Independence Party candidate for governor in 2010, waded back into governor's race politics on Tuesday when he endorsed GOP candidate Jeff Johnson in his challenge to incumbent DFL Gov. Mark Dayton.

"I believe Jeff will bring to government a commitment to accountability that's sorely missing," Horner said, standing alongside Johnson at a Capitol news conference. "We have too many examples of this governor's after-the-fact criticism of legislation and policies that he championed and signed into law."

Asked for an example of that, Horner cited the Vikings stadium bill that Dayton signed in 2012 that allowed the team to amass significant revenue by selling so-called "seat licenses." Dayton, Horner said, "claimed he didn't know that was in it."

Dayton brushed off Horner's criticisms and his endorsement of Johnson. "He didn't support me in 2010 so I'm not surprised," Dayton said. Of Johnson, he said, "he said he's proudly part of the tea party, and now he's joining up with the Independence Party. I guess he's trying to broaden his appeal."

Horner is a former Republican operative who later co-founded a successful Twin Cities public relations firm. In 2010, he left the GOP and embraced the Independence Party, the one-time political home of former Gov. Jesse Ventura.

Running against Dayton and GOP candidate Tom Emmer that year, Horner captured 12 percent of the vote with a message of fiscal discipline and social moderation. Dayton beat Emmer by a thin margin of about 9,000 votes, and some Republicans suggested Horner's candidacy was partly responsible. Horner had secured endorsements from a number of prominent retired Republican politicians, including former governors Arne Carlson and Al Quie.

That led then-GOP state chairman Tony Sutton to brand such Republicans "quislings," a reference to a World War II-era Nazi appeaser. The GOP Central Committee met to officially strip Carlson and Quie of their party membership.

"Our party shouldn't have done that," Johnson said Tuesday. "That was a mistake."

Horner said he continued to occasionally interact with the Independence Party as recently as earlier this year. But he said this year's IP candidate, Hannah Nicollet, is not mounting a viable campaign. Nicollet failed to raise enough campaign funds to qualify for a public campaign subsidy that would have given her a much-needed financial boost.

"I've never even met Tom Horner," Nicollet said. "If he likes Jeff Johnson's vision, that's his prerogative."

Nicollet said she is confirmed to participate in the first of five gubernatorial debates, on Oct. 1 in Rochester, and that she hoped to participate in the four other scheduled debates in the race. Nicollet also said she hoped to start releasing ads online in the next week or two.

If neither Nicollet nor the other IP statewide candidates are able to muster more than 5 percent of the vote in their races this November, the party would lose its status as a major party under Minnesota law.