Republican Gov. Sarah Palin of Alaska stunned her state and the political world Friday by announcing she will resign her post at the end of the month, igniting speculation about what the move means for her political future and her viability for the GOP's presidential nomination in 2012.
The decision, announced in a hastily called lakeside briefing at her Wasilla, Alaska, home, sparked sharply diverging reactions over its impact on the future of the polarizing Mrs. Palin, the 2008 GOP vice presidential nominee who remains a very popular figure with much of the conservative Republican base.
Comparing herself to a basketball point guard passing the ball to a teammate, Mrs. Palin said, "I am determined to take the right path for Alaska even though it is unconventional and not so comfortable."
Some called the decision to resign a canny strategic move that takes Mrs. Palin out of the line of fire and clears her schedule for a presidential run, some theorized the governor had simply grown sick of politics and personal attacks, while others warned that quitting with more than a year left in her term would prove disastrous - perhaps even fatal - for Mrs. Palin's political future.
Mrs. Palin said that she will step down July 26, with Lt. Gov. Sean Parnell, who was at her side at the press conference, taking over as governor.
Mr. Parnell called Mrs. Palin's decision "selfless" and said he would work with her staff for "a seamless transition." She did not take questions from the few Alaska reporters who made it to Wasilla and only cryptically referred to her future plans.
Democrats immediately pounced on the news.
"Either Sarah Palin is leaving the people of Alaska high and dry to pursue her long-shot national political ambitions or she simply can't handle the job now that her popularity has dimmed and oil revenues are down," said Democratic National Committee spokesman Brad Woodhouse.
One of Mrs. Palin's political rivals did not parse words in a terse statement sent after midnight.
I am deeply disappointed that the governor has decided to abandon the state and her constituents before her term has concluded, said Sen. Lisa Murkowski, Alaska Republican.
Decrying what she has called politically motivated attacks on her family and her ethics, 45-year-old Mrs. Palin in a lengthy, at times rambling statement said she would rather "effect positive change outside government at this moment in time on another scale and actually make a difference for our priorities."
Shortly after concluding her statement, the governor sent out a Twitter message to supporters that read: "We'll soon attach info on decision not to seek re-election. ... This is in Alaska's best interest, my family's happy. ... It is good, stay tuned."
Jason Recher, an aide who worked for Mrs. Palin during last year's campaign, said the environment in Alaska had changed so much since August "with the influx of the national anti-Republican, anti-Palin movement - it's been like an avalanche."
"With all the frivilous ethics complaints, it just had become completely unsustainable for her to be governor," he said.
The stunning move is certain to scramble political calculations for the Republican presidential field for 2012. Many had expected Mrs. Palin to announce she would not seek re-election but would serve out her term, which ends in December 2010.
The decision to leave before she had completed her first term is perplexing because her limited experience in a high-level political post was something critics saw as her weakness as Arizona Sen. John McCain's running-mate last year. Many political handicappers thought she needed to build up a record of accomplishment in office before reaching again for higher office.
Ralph Seekins, a Republican National Committee member from Alaska and friend of both Mrs. Palin and her husband, called the governor's timing "odd," announcing a momentous decision the day before the Fourth of July.
Asked whether he thought financial considerations were behind the move, Mr. Seekins said Mrs. Palin "apparently had a good book deal and may need to devote time to getting the book finished for publication, though she has raised considerable sums for her legal defense fund."
Some analysts saw the move as classic Sarah Palin - confounding Washington's so-called beltway insiders but one that will play well outside the beltway.
University of Alaska Fairbanks political scientist Jerry McBeath said Mrs. Palin's gambit could benefit both her and the state.
"Alaska is an isolated stage from which to operate if you want to figure in American national politics," he told the Associated Press. "I don't know what she has in mind. Some TV show or some national radio show. There are opportunities for her, I'm sure."
But others, including veteran political analyst Larry Sabato and Republican strategist Ed Rollins, said they were dumbfounded by the resignation move.
Mr. Rollins called Mrs. Palin in an interview with CNN " a shooting star" that "just crashed to earth."
Mr. Recher sees it differently.
The governor's colorful private life, the media soap opera surrounding her family and her at-times turbulent relations with Mr. McCain and the Washington establishment also may have played a role in Friday's drama.
Mrs. Palin referred in her remarks to months of politically inspired attacks on ethical issues, attacks she said left her and husband Todd Palin facing $500,000 in legal bills. She was also the subject of a fierce personal assault by mostly unnamed critics in a massive profile in Vanity Fair magazine.
Last month, she generated headlines again in a clash with late-night comedian David Letterman over an off-color joke Mr. Letterman told about the governor's daughter - for which he apologized later - and for skipping out on a commitment to be the keynote speaker at a Republican fundraising dinner for the House and Senate campaign committees.
In her announcement, Mrs. Palin said it "hurts to make this choice," but compared herself to a point guard in basketball, a position she herself excelled at in high school.
"A good point guard knows exactly when to pass the ball so the team can win," she said. "I know when it is time to pass the ball for victory." She added the decision to step down had been "in the works for a while."
After first intending to step down next year, Mrs. Palin said she concluded it was better for the state if she resigned immediately.
"Once I decided not to run for re-election, I also felt that to embrace the conventional lame-duck status in this particular climate would just be another dose of politics as usual, something I campaigned against and will always oppose," she said.
After a lengthy recital of her achievements as governor, Mrs. Palin bemoaned the amount of time and resources she had to devote to personal legal battles and overcoming negative press coverage.
"You are naive if you don't see a full-court press on a national level" attacking her, she said, appealing to Alaskans. "All I can ask is that you trust me with this decision."
Mrs. Palin remains one of her party's most charismatic figures and one of its most sought-after speakers 11 months after she burst onto the national political scene when Mr. McCain tapped her as his vice-presidential choice.
She proved a potent draw among the Republican faithful, but Mr. McCain's selection was also criticized by some, and she was the target of ridicule in devastating "Saturday Night Live" sketches by comedian Tina Fey.
Since then, Mrs. Palin has remained popular with the grass-roots of her party, especially among social conservatives, though lately she has come under sharp attack from some of Mr. McCain's top campaign aides as someone who proved unready for the rough-and-tumble of national politics in last year's race.
She has run a gauntlet of ethics investigations sought by state Democrats in the past few months, though all charges to date have been dismissed.
Still, she was said to be frustrated about being tied down to the governorship while other rivals for the presidential nomination, including former Massachusetts Gov. Mitt Romney, were able to campaign full time.
In a statement released by his office, Mr. Romney said, "I wish Sarah Palin and her family well, and I know that she will continue to be a strong voice in the Republican Party."
Republican National Committee Chairman Michael S. Steele said he would be "talking to Governor Palin very soon. She is an important and galvanizing voice in the Republican Party. I believe she will be very helpful to the party this year as we wage critical campaigns in Virginia and New Jersey."
Mrs. Palin's decision to step down as governor follows the announcement June 2 by Republican Gov. Tim Pawlenty of Minnesota that he would not run for a third term next year. Mr. Pawlenty has also been mentioned as a possible candidate for president in 2012.
While not detailing her plans, Mrs. Palin has been building up her political warchest in recent days, even as speculation over her political future mounted.
The Anchorage Daily News reported earlier this week that SarahPAC, the governor's political action campaign, sent out an e-mail seeking new contributions from supporters, in part to boost Mrs. Palin's fundraising totals ahead of the June 30 reporting deadline to the Federal Election Commission.
"With your help, we can take the governor's message and encourage others who also have hope and are firmly rooted in the conservative belief that you know best how to spend your money and not government," wrote SarahPAC spokeswoman Meghan Stapleton in the e-mail solicitation.
• Christina Bellantoni, Ralph Z. Hallow and Joseph Curl contributed to this report.