WASILLA, Alaska (AP) — Alaska Gov. Sarah Palin made a surprise announcement Friday that she is resigning from office at the end of the month without explaining why she plans to step down, raising speculation that she would focus on a run for the White House in the 2012 race.

The former Republican vice presidential candidate hastily called a news conference Friday morning at her home in suburban Wasilla, giving such short notice that only a few reporters actually made it to the announcement. State troopers blocked late-arriving media outside her home, and her spokesman, Dave Murrow, finally emerged to confirm that Palin will step down July 26. He refused to give details about the governor’s future plans.

“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,” Palin said in a statement released by her office.

Lt. Gov. Sean Parnell will be inaugurated at the governor’s picnic in Fairbanks at the end of the month, Murrow said.

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

Palin said she planned to make a “positive change outside government,” without elaborating. She also expressed frustration with her current 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.

Later, on Twitter, she promised supporters more details: “We’ll soon attach info on decision to not seek re-election ... this is in Alaska’s best interest, my family’s happy ... it is good. Stay tuned”

Palin’s decision even took Parnell by surprise. He said he was told on Wednesday evening, and was not aware that any presidential ambitions were behind the move.

Palin emerged from relative obscurity nearly a year ago when she was tapped as then Republican presidential candidate John McCain’s running mate.

She was a controversial figure from the start, with comedian Tina Fey famously imitating her elaborate hairstyle and folksy “You betcha!” on “Saturday Night Live.”

Most recently, she led a public spat with “Late Show” host David Letterman over a joke he made about one of her daughters being “knocked up” by New York Yankees baseball player Alex Rodriguez during the governor’s recent visit to New York. Palin’s 18-year-old daughter, Bristol, is an unwed, teenage mother.

Letterman later apologized for the joke.

Palin’s family and the ridicule they endure being in the public eye was part of her decision. She complained that her 14-month-old son, Trig, who was diagnosed with Down’s syndrome, had been “mocked and ridiculed by some mean-spirited adults recently.” She didn’t elaborate.

Palin campaigned on ethics reform in the 2006 election, defeating incumbent Gov. Frank Murkowski in the Republican primary and a former two-term Democratic governor, Tony Knowles, in the general election.

She enjoyed an extended honeymoon with lawmakers and voters alike. Her popularity was in the 80 percentile range, even though that fell after the bruising, partisan presidential campaign.

Palin’s delivery of two weeks’ notice rattles a Republican Party plagued with setbacks in recent weeks, including extramarital affairs disclosed by two other 2012 presidential prospects, Nevada Sen. John Ensign and South Carolina Gov. Mark Sanford.

Ensign, a member of the Christian ministry Promise Keepers, stepped down from the Senate Republican leadership last month after admitting he had an affair for much of last year with a woman on his campaign staff who was married to one of his Senate aides. Ensign later disclosed he had helped the woman’s husband get two jobs during the affair.

A government watchdog group, Citizens for Responsibility and Ethics in Washington, wants the Senate ethics committee and the Federal Election Commission to investigate.

Just days after news of Ensign’s affair broke, Sanford admitted an affair with a woman in Argentina. Some lawmakers are now calling for his resignation. Before the admission, Sanford had been missing from the state for five days visiting his lover. He had slipped his security detail, lied to his staff about where he was and failed to transfer power to the lieutenant governor in case of a state emergency.

Sanford admitted he also saw the mistress during a state-funded trip to Argentina last year. He promised to reimburse the state for part of the trip’s costs. The state Commerce Department said the trip itinerary originally included only Brazil, but the governor requested economic development meetings in Argentina.

The GOP troubles seem to have left two prominent 2012 prospects, former House Speaker Newt Gingrich and 2008 presidential hopeful Mitt Romney, unscathed, however.