Democrat Russ Feingold has decided he will not be a candidate for political office next year, taking himself out of the running in 2012 for either U.S. senator or for governor in the event Democrats force a recall election against Republican Gov. Scott Walker.

In an email going out to supporters early Friday morning, Feingold called it a difficult decision but said he wanted to devote his time to teaching full time at Marquette Law School, finishing the book he is writing on the U.S. response to the Sept. 11 attacks and leading the political committee he founded, Progressives United.

"While I may seek elective office again someday, I have decided not to run for public office during 2012," Feingold said in the email.

Some Democrats were looking to Feingold as perhaps their leading candidate against Walker next year in the event of a successful recall drive. His announcement ends that scenario.

Feingold's lack of interest in running for Senate is not a big surprise.

Since he was defeated in 2010 in his bid for a fourth term, he has sent no obvious signals about a quick return to the legislative body where he served for 18 years.

"After twenty-eight continuous years as an elected official . . . I have found the past eight months to be an opportunity to look at things from a different perspective," Feingold said in the email, saying he was "thoroughly enjoying the life of a private citizen."

His decision leaves the Democratic Senate field wide open, though many Wisconsin Democrats will now regard U.S. Rep. Tammy Baldwin, with her political base in vote-rich Dane County, as the early favorite for the party nomination.

Both parties next year will be fiercely contesting the seat, which will be vacated with the planned retirement of four-term Senate Democrat Herb Kohl.

Feingold would have been the strong favorite to win the Democratic Senate nomination.

In Senate numbers released Thursday by the Democratic survey firm of Public Policy Polling, the pollsters described Feingold as the "best-known and best-liked" of several would-be candidates, including Republican ex-Gov. Tommy Thompson, former GOP congressman Mark Neumann, Baldwin and two other Democrats: U.S. Rep. Ron Kind and former congressman Steve Kagen.

Feingold did the best among the four Democrats in that group in head-to-head matchups with Republicans, running ahead of Neumann and essentially even (48% to 47%) against Thompson. The survey of 830 Wisconsin voters was taken Aug. 12-14, with a margin of error of plus or minus 3.4 percentage points.

"Republicans have a genuine pick-up opportunity here. As the recall elections showed, this is a very closely divided state right now," said PPP pollster Dean Debnam.

In his email, Feingold said he would be focused going forward on the self-described mission of his political committee, curbing corporate influence in politics. "The entire political climate is more infected by the domination of very wealthy individual and corporate interests than perhaps at any time in our nation's history," he said.