"After much prayer and serious consideration, I have decided that I will not be seeking the 2012 GOP nomination for president of the United States," ABC News reported the 2008 vice presidential nominee wrote in the letter.
"As always, my family comes first and obviously Todd and I put great consideration into family life before making this decision. When we serve, we devote ourselves to God, family and country. My decision maintains this order. …
"I believe that at this time I can be more effective in a decisive role to help elect other true public servants to office -- from the nation's governors to congressional seats and the presidency. 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."
Palin said she will keep campaigning for "freedom and free markets" and "energy independence through domestic resource developments of conventional energy sources, along with renewables."
She also said taxes and regulations that "kill American industry" must be reduced and government "minimized."
"Know that by working together we can bring this country back -- and as I've always said, one doesn't need a title to help do it," Palin wrote.
A poll published Tuesday indicated two-thirds of Republicans said they don't want Palin to run, Politico said.
"She stirs up a lot of conservatives in the base, but I don't think conservatives are looking to her as a presidential nominee who can save the conservative movement," conservative activist Chuck Muth said. "What niche in the conservative movement does Sarah Palin fill that's not already filled by one of the other candidates?"