Gov. Sarah Palin of Alaska abruptly announced on Friday she is quitting her job at the end of the month, shocking Republicans across the country and leaving both parties uncertain about whether she is leaving national politics or laying the groundwork for a presidential run.

Palin, 45, the Republican vice-presidential nominee last year, was supposed to serve through the end of 2010; she said she would cede control of the state to Lt. Gov. Sean Parnell on July 26.

Speaking outside her home in Wasilla, she offered conflicting signals about her intentions.

In her tone and some of her words as she made the announcement in an often-rambling address, Palin sounded like someone making a permanent exit from politics after what her friends have described as a rough and dispiriting year.

But in the course of her remarks, delivered in a voice that often seemed rushed and jittery, she sounded at times like a candidate with continued national aspirations, as when she suggested she could "fight for all our children's future from outside the governor's office."

Palin said she had decided not to seek re-election when her term expires at the end of next year and that, given that, she did not think it was fair to her constituents to continue in office.

"As I thought about this announcement that I would not seek re-election," she said, "I thought about how much fun other governors have as lame ducks: They maybe travel around their state, travel to other states, maybe take their overseas international trade missions."

"I'm not going to put Alaskans through that," she said. "I promised efficiencies and effectiveness. That's not how I'm wired. I'm not wired to operate under the same old politics as usual."

The news conference came at the end of a week in which a Vanity Fair article about Palin brought renewed focus on many of the criticisms of her as a candidate for vice president under Sen. John McCain and set off a new round of recriminations among McCain's advisers about her competence.

But while Palin has been derided by much of the Republican Party elite, she remains extremely popular with many grass-roots members of the party, especially social and religious conservatives, who see her as a principled and appealing standard-bearer for their values.

Palin's announcement was another unusual marker in what has been a tumultuous year for this first-term governor since McCain turned her into a national figure overnight by shocking his own party and naming her his running mate. It also underscored the instability within the Republican Party as it tries to find a strategy and voice in the wake of losses in 2008.