(CNN) -- Sarah Palin, ending months of speculation, said Wednesday she will not run for president, either as a Republican or third-party candidate.
"This has been prayerfully considered," the former Alaska governor said on the Mark Levin radio program. "I can be on the right path without being a candidate."
Palin previously said she was still considering a run, but she faced an October 28 filing deadline for the first-in-the-nation primary in New Hampshire.
"It's a life-altering proposition and she really spent a lot of time talking with her family and being with her family," said a source close to the Palin family. "I think it's pretty straightforward."
Palin vaulted to political stardom when she was chosen as Republican Sen. John McCain's running mate in the 2008 presidential election. McCain was defeated by then-Sen. Barack Obama.
She has become a lightning rod for criticism in some circles, while others champion her conservative values. She has often been praised by GOP presidential hopefuls.
A CNN/ORC International Poll of registered voters in late September showed Palin trailing Obama in a hypothetical 2012 general election matchup, 58% to 37%. The poll had a sampling error of plus or minus 3 points.
Palin's announcement settles the GOP field. New Jersey Gov. Chris Christie announced Tuesday he will not seek the GOP nomination.
"As always, my family comes first and obviously Todd and I put great consideration into family life before making this decision," Palin said in a written statement. "When we serve, we devote ourselves to God, family and country. My decision maintains this order."
The director of "The Undefeated," a biopic that lauded Palin, said he was not surprised.
The decision makes the 2012 presidential campaign "much less interesting," said Stephen K. Bannon.
Palin could have been like Ronald Reagan in 1976, in that her voice was the best voice to challenge the establishment, Bannon told CNN. Reagan unsuccessfully sought the GOP nomination that year, but he brought a voice to party conservatives.
Palin thanked supporters and said she will concentrate on helping other leaders and candidates.
"We need to continue to actively and aggressively help those who will stop the 'fundamental transformation' of our nation and instead seek the restoration of our greatness, our goodness and our constitutional republic based on the rule of law," she said in the statement.
CNN's Peter Hamby contributed to this report.