"What seemed to weigh heavily upon her was the cost associated with all the records request, ethics complaints, the cost of staff time, the distractions," Parnell told ABC News. "We are up to $2 million in costs to Alaskan taxpayers for that and I think there was just that sense that that was a burden to moving Alaska forward."
Palin's political opponents like Alaska senator and fellow Republican Lisa Murkowski have criticized Palin's unexpected decision.
"I am deeply disappointed that the governor has decided to abandon the state and her constituents before her term has concluded," Murkowski said.
Sen. John McCain, R-Ariz., the man who launched her to the national stage by selecting her not quite a year ago as his running mate, was more gracious, saying Saturday Palin "will continue to play an important leadership role in the Republican party."
But other Republicans were more blunt in their critiques. Former Bush administration advisor Karl Rove said, "If she wanted to escape the ethics investigations and save the taxpayers money, she's now done that, but it is -- it sort of sent a -- sent a signal that if you do this kind of thing to a sitting governor like her, you can drive her out of office," Rove said on Fox News Sunday. "Also, she's not going to be able to escape media attention. If she thinks somehow that she's going to be able to protect her family against the kind of things that she's suffered over the last couple of months from David Letterman and others, and seek a role of leadership for effective change for our country, as she said in her speech, she's not going to be able to do it."
And former Arkansas Gov. Mike Huckabee and potential 2012 contender himself said, "The challenge that she's going to have is that there will be people who say, 'Well, look, you know, if they chase you out of this, it won't get any easier for you at other levels of the stage.'"
Of her future plans, Palin, 45, said in her Friday announcement, "I will support others who seek to serve, in or out of office, for the right reasons, and I don't care what party they're in or no party at all. Inside Alaska -- or outside Alaska."
A source close to Palin told ABC News she will raise money for other political candidates and causes, give speeches and write a book.
As for one hint of ambitions outside Alaska, Palin's camp says she already has plans to speak in the lower 48 states, including a women's event in Simi Valley, Calif., next month.
But the source insisted that her decision was solely about whether to run again for governor of Alaska, separate and apart from any future political ambitions. She wanted to get away from bitter politics and stop wasting taxpayer money to fight baseless ethics complaints, the source said
"She has made no decision on whether to run for president in 2012," the source said of a decision that will come later.
ABC News political analyst Cokie Roberts said that leaving her responsibilities as governor of Alaska could free Palin up to focus on a national campaign.
"Gov. Palin can spend full time for the next couple of years on the road, helping Republican candidates, shoring up her support inside the party, appearing on television, radio and newspaper interviews and becoming a national figure. She won't have to be spending her time in Juneau worrying about the state budget."