In a news conference on Friday from her Wasilla, Alaska, home, the first-term GOP governor said she was yielding her office soon to Lt. Gov. Sean Parnell, also a Republican, adding, "This decision has been in the works for awhile," and, "I'm not wired to operate under the same old politics as usual."
Palin, 45, did not take questions after her announcement, but compared herself to a good basketball point guard facing "a full court press from the national level."
"She knows exactly when to pass the ball so that a team can win," Palin said.
Palin's decision not to run for re-election was not a bombshell on its own but, rather, her choice to resign at the end of the month was seen as a curve ball.
Indeed, many analysts believed it would have been tough for her to win re-election in November 2010 in Alaska and then try to campaign in states like Iowa, New Hampshire and South Carolina if Palin has aspirations for the 2012 presidential race.
The logistics of dealing with an Alaska legislative season in 2011 while spending time campaigning in the lower 48 would have been daunting, analysts say.
Gerry McBeath, a political science professor at the University of Alaska-Fairbanks, said Palin still appears to be an attractive political figure on a sparse Republican presidential landscape.
"From what we know right now," McBeath told ABC News Radio, "she's not under any major investigation. There have been a minor series of ethical flaps, mostly from opposition figures in the state."
Even so, the breathless and sudden delivery of Palin's announcement prompted some puzzled reactions among analysts.
"It's mystifying," said ABC News political analyst Cokie Roberts. "It was a bizarre statement. It didn't make a lot of sense, and it doesn't seem to be the kind of thing someone would do if someone was running for president."
But Fred Malek, a veteran Republican operative and Palin adviser, told ABC News that Palin intends to continue to be helpful to other Republicans and is leaving her political options open.
"She's not going to go hide in a cave," Malek said. "She'll continue to be a major friend and force for Republican figures in this country."
Malek said Palin is not ruling out a return to politics, although she has no plans on the horizon to seek another office.
Other supporters were equally upbeat about her future.
"People here are collectively agreeing that it sheds everything she doesn't like about running government now and allows her to devote fulltime to this passion she has about wanting to lead the country away from socialism," said Alaska legislative aide Larry Persily, who worked with the governor in Alaska, and later as her representative in Washington, D.C.
The McCain campaign did not immediately comment Friday, though McCain himself issued a written statement Saturday.
"I have the greatest respect and affection for Sarah, [her husband] Todd, and their family," McCain said. "I was deeply honored to have her as my running mate and believe she will continue to play an important leadership role in the Republican Party and our nation."
Earlier this week, Palin and her political operation were portrayed in an unflattering light in the latest issue of Vanity Fair.
Purdum wrote that it appears Palin has few friends left among the political team assigned to her by the McCain's campaign.