WASILLA, Alaska - Alaska Gov. Sarah Palin abruptly announced Friday that she is resigning from office at the end of the month, a shocking move that rattled the Republican Party but left open the possibility that she would seek a run for the White House in 2012.

Palin, 45, and her staff kept her plans shrouded in mystery, and it was unclear if the controversial hockey mom would quietly return to private life or begin laying the foundation for a presidential bid.

Palin said she planned to make a "positive change outside government," without elaborating.

Palin's spokesman, David Murrow, said the governor didn't say anything to him about this being her "political finale." He said he interpreted Palin's comment about working outside government as reflecting her current job only.

"She's looking forward to serving the public outside the governor's chair," he said.

Pam Pryor, a spokeswoman for Palin's political action committee, SarahPAC, said the group continues to accept donations on its Web site, with an uptick in funds after Palin's announcement.

The announcement caught even current and former Palin advisers by surprise. Former members of the John McCain campaign team, now dispersed across the country, traded perplexed e-mails and phone calls.

Personal pressures have been mounting - scrutiny on her family, legal bills, ethics investigations and a running, public fued with McCain's camp that has flared up again.

In a hastily arranged news conference at her home in Wasilla, Palin said she will formally step down July 26, and Lt. Gov. Sean Parnell will be inaugurated at the governor's picnic in Fairbanks. Palin said she had decided against running for re-election as Alaska's governor and believed it was best to leave office even though she had two years left in her term.

"Many just accept that lame-duck status, and they hit that road. They draw a paycheck. They kind of milk it. And I'm not going to put Alaskans through that," she said.

The 2008 vice presidential nominee was seen as a likely presidential contender in 2012 and had proved formidable among the party's base. But the last week brought a highly critical piece in Vanity Fair magazine, with unnamed campaign aides questioning if Palin was ever really prepared for the presidency.

The backbiting continued with follow-up articles recounting the nasty infighting that plagued her failed bid. Her advisers sniped with other Republicans, underscoring the deeply divided GOP looking for its next standard bearer.

Meghan Stapleton, Palin's personal spokeswoman, shot down speculation that ranged wildly from Palin dropping out of politics altogether to eyeing runs against fellow Alaska Republicans U.S. Rep. Don Young and U.S. Sen. Lisa Murkowski. Palin's comment about serving outside government refers to the present, she said.

Stapleton, however, said it's too early to say whether Palin would seek the presidency. In the meantime, the governor will continue to work "toward affecting positive change as a citizen without a title right now," she said.

Palin's resignation, timed on the eve of the July 4 holiday when many Americans had already begun a three-day weekend, seemed designed to avoid publicity. She alluded to how she could help change the country and help military members - code that she didn't think her time on the national stage was over.

Palin said her family weighed heavily in her decision.

"I polled the most important people in my life, my kids, where the count was unanimous," she said. "Well, in response to asking, 'Hey, you want me to make a positive difference and fight for all our children's future from outside the governor's office?' It was four yeses and one 'Hell, yeah!' And the 'Hell, yeah' sealed it."

Palin's decision not to seek re-election was a familiar one for a potential presidential candidate. Former Massachusetts Gov. Mitt Romney chose not to seek another term as he geared up for an unsuccessful 2008 presidential bid. Minnesota Gov. Tim Pawlenty has announced he won't seek another term, giving him plenty of free time ahead of a potential 2012 bid.

Fred Malek, a Republican strategist who has advised Palin over the past year, said Palin was "really unhappy with the way her life was going."

"She felt that the pressures of the job combined with her family obligations and the demands and desires to help other Republican candidates led her to decide not to run again. Once that decision was made, she realized, why not do it now and let the lieutenant governor take over and get a head start on his election," Malek said.

Palin's move also prompted speculation among bloggers and critics that the governor was facing a looming political crisis or embarrassment.

"There's got to be something below the surface that's about ready to come to the surface that quite potentially she just didn't want to deal with as governor," said Andrew Halcro, a Palin critic who lost the 2006 gubernatorial race to her.

There is, for example, a pending public records request from Linda Kellen Biegel, an Anchorage blogger who is seeking e-mails showing an effort by the Palin administration to smear her critics, including those filing ethics complaints against the governor. Biegel, whose own ethics complaint was dismissed, also is seeking an investigation into the financial profits to the Palin family from racing sponsors of Palin's husband, Todd, in the 2,000-mile Iron Dog snowmobile race.

"There may be embarrassing things in there. I don't know," Biegel said. "I'm just as baffled as a lot of people."

Stapleton, Palin's spokeswoman, dismissed the rumors of damaging news on the horizon.

"No truth whatsoever. Period," she wrote in an e-mail to The Associated Press. "Just more nonsense from the same people who choose to waste state resources."

Palin was first elected in 2006 on a populist platform. But her popularity has waned as she became embroiled in partisan politics following her return from the presidential campaign. Her term would have ended in 2010.

Palin expressed frustration with her role as governor.

"I cannot stand here as your governor and allow the millions of dollars and all that time go to waste just so I can hold the title of governor," Palin said, referring to the alleged impact of multiple ethics complaints against her, most of which have been dismissed.

Palin has the potential to make far more money in the private sector than the $125,000 or so she has been making as governor.

Palin already had a deal with publisher HarperCollins to produce her memoir, with publication planned for next spring. Terms of the deal have not been disclosed. Six-figure book deals are common for high-profile political figures.