Huckabee, the former Arkansas governor, joins Mississippi Gov. Haley Barbour, South Dakota Sen. John Thune and Indiana Rep. Mike Pence on the sidelines. His decision underscores that for all of Obama's vulnerabilities on the economy, taking on his re-election machine and potential $1 billion treasure chest remains a daunting task.
The 55-year-old Baptist minister insists that he could have captured the GOP nomination, citing polls that showed he could score strong even in the Northeast and among the less conservative rank-and-file party members.
"All the factors say go, but my heart says no," Huckabee said Saturday night on his Fox News Channel show.
"Only when I was alone, in quiet and reflective moments, did I have not only clarity but an inexplicable inner peace," he said. "Being president is a job that takes one to the limit of his or her human capacity. For me, to do it apart from the inner confidence that I was undertaking it without God's full blessing is simply unthinkable."
The announcement makes an already wide-open Republican field even more unpredictable.
Former House speaker Newt Gingrich has been making a concerted effort to reach out to the right. Although he's been noting his recent conversion to Catholicism, he's hampered by two divorces and an adulterous history. Former Massachusetts governor Mitt Romney must explain his change of heart over the years on positions on guns, gay rights and abortion; health care also is a problem for him. Minnesota's ex-governor, Tim Pawlenty, has had to apologize for backing climate change legislation.
With social conservatives looking for a home, the void created by Huckabee's decision could prompt 2008 vice presidential candidate Sarah Palin or Minnesota Rep. Michele Bachmann to run.
Republican candidates were quick to praise Huckabee after his announcement.
"His voters are very independent, and they're going to go where they believe that America needs to go both in conservative and spiritual values," Gingrich said. "Gov. Huckabee is going to remain a very important figure in the conservative movement and I suspect that he's going to have a role to play for years to come."
Pawlenty said he'd work hard to gain the support of millions of Americans who have backed Huckabee, while former Pennsylvania Sen. Rick Santorum praised the TV host for praying before deciding not to run. Santorum added that he wanted to talk with Huckabee about fighting for traditional values even as some Republicans "seek to form a 'truce' on social issues."
That was a slap at Daniels, who is considering a run and has suggested that Republicans downplay their focus on cultural issues like abortion while the nation's economy is so fragile.
Huckabee praised several potential GOP nominees who, he said, hold points of view similar to his own. A notable omission from the list: Romney.
"There has been a lot of talk about Mitt Romney and me. And we don't socialize together. We're not close, you know, in personal ways," Huckabee said. "But I want to make it very clear today, if Mitt Romney is the nominee for our party, I will support him because I believe that Mitt Romney would be a better president of the United States than Barack Obama on any day."
Had he chosen to run, Huckabee would have been forced to give up the lucrative media career he's enjoyed since his unsuccessful presidential bid four years ago. In addition to his TV show, he hosts a nationally syndicated radio program, gives paid speeches around the country and has even launched a series of animated videos for children on American history.
"I just somehow believe deep within me that it wasn't the right time and it wasn't to be," he said Sunday.
The former governor said raising the necessary cash to run for president wasn't an issue in his decision, though it may play a major part for others. One candidate who wouldn't have that problem is Trump, the billionaire real estate tycoon and reality TV star who's been toying with the idea of a Republican run.
"Mike, enjoy the show," Trump said in an on-air message on Fox, directly after Huckabee's announcement. "Your ratings are terrific. You're making a lot of money. You're building a beautiful house in Florida. Good luck."
That was one of two messages Trump taped ahead of Huckabee's announcement, the former governor said Sunday. The other would have followed a decision to run for the nomination, he said, but he didn't reveal its contents.