Ron Carey, a former chief of staff to Bachmann, said he suspects she was anticipating a tough battle ahead and seemed to be stuck in place in Congress.
"This is a great chance to exit stage right rather than have a knockdown, drag-out re-election fight," said Carey, also a former state GOP chairman. "The reality also set in that she is not a favorite of Republican leadership, so she is not going to be rising up to a committee chair or rising up in leadership."
Her departure next year is part of a larger shift involving the leading personalities of the tea party. Stalwarts like former Alaska Gov. Sarah Palin, former Rep. Allen West of Florida and former South Carolina Sen. Jim DeMint have left elected office to move into conservative organizations and commentary roles.
They've been replaced by a new round of tea party-backed lawmakers such as Sens. Ted Cruz of Texas and Mike Lee of Utah and Rep. Raul Labrador of Idaho.
"The movement had moved past her to a new round of leaders in Congress and the states around the country," said Dick Wadhams, a Colorado-based Republican strategist. "In a short period of time, a new generation has stepped forward since the last election."
Bachmann also said her decision "was not impacted in any way by the recent inquiries into the activities of my former presidential campaign" last year. In January, a former Bachmann aide filed a complaint with the Federal Election Commission, claiming the candidate made improper payments to an Iowa state senator who was the state chairman of her 2012 presidential run. The aide, Peter Waldron, also accused Bachmann of other FEC violations.
Bachmann had given few clues she was considering leaving Congress. Her fundraising operation was churning out regular pitches for the small-dollar donations that she collected so well over the years. She also had an ad running on Twin Cities television promoting her role in opposing President Barack Obama's health care overhaul. The early timing of the ad suggested she was preparing for a tough fight against Democrat Jim Graves, a hotel chain owner who narrowly lost to Bachmann in November.
Without the polarizing Bachmann on the ticket, Republicans could have an easier time holding a district that leans more heavily in the GOP direction than any other in Minnesota. A parade of hopefuls was expected.
By Wednesday morning, state Rep. Matt Dean, a former House majority leader, said he was inclined to run.
"It is something I have thought about in the past if Michele were to not run again," Dean said. "It's not something that I just started thinking about this morning."
Graves said he thought Bachmann had "read the tea leaves."
"The district is changing," the Democrat said in an interview Wednesday with Minneapolis television station KARE. "They want somebody who really does have some business background and understands the economy and can get things done in Washington and back in the district."
Andy Aplikowski, who has long been active in the district's Republican Party chapter, said he expected Bachmann to run again but can understand why she didn't.
"It's a grueling thing to be in Congress. It's a grueling thing to be Michele Bachmann in Congress," he said. "Every move you make is criticized and put under a microscope."
Bachmann's strongly conservative views propelled her into politics, and once there, she never backed down.
She was a suburban mother of five in 1999 when she ran for a Minnesota school board seat because she thought state standards were designed to teach students values and beliefs.
She lost that race, but won a state Senate seat a year later. Once in St. Paul, she seized on gay marriage as an issue and led a charge to legally define marriage in Minnesota as between one man and one woman. That failed, but Bachmann had laid the foundation with social conservatives to help propel her into Congress in 2006.
In Washington, she turned to fiscal issues, attacking Democrats and President Barack Obama for government bailouts and the health care overhaul. Even in her early years in Congress, Bachmann frequently took those views to right-leaning cable talk programs, cultivating her national image as she built a formidable fundraising base with like-minded viewers outside Minnesota.
But her penchant for provocative rhetoric sometimes backfired. She was hammered in 2008 for saying Obama might have "anti-American views," a statement that prompted a rare retreat by Bachmann and made her race that year closer than it would have been. She was also criticized by her fellow Republicans last July for making unsubstantiated allegations that an aide to Secretary of State Hillary Rodham Clinton had family ties to Egypt's Muslim Brotherhood.
Her White House bid got off to a promising start, with a win in an Iowa GOP test vote. But Bachmann quickly faded and finished last when the real voting started in Iowa's leadoff caucuses, a result that caused her to drop out. Saddled with debt, she opted to campaign again for her Minnesota seat and squeaked through.
But the failed presidential campaign continued to dog her. Allegations of improper payments prompted ethics inquiries. Bachmann also faced a lawsuit from a former aide that alleged someone on the congresswoman's team stole a private email list of home-school supporters for use in the campaign. That case is pending.
On Wednesday, Bachmann promised supporters she would "continue to work overtime for the next 18 months in Congress defending the same Constitutional Conservative values we have worked so hard on together."
As for her plans beyond Congress, she said, "There is no future option or opportunity, be it directly in the political arena or otherwise, that I won't be giving serious consideration if it can help save and protect our great nation."
Bachmann's success in the talk media world led industry analysts to say she could easily move into a gig as a host. She has been mentioned as a potential challenger to first-term Democratic Sen. Al Franken but has given little indication that she would take that step.
Thomas reported from Washington. Associated Press writer Lou Kesten contributed.