WASHINGTON (AP) — Mike Huckabee's decision to forgo a shot at the U.S. presidency further muddies the field for a worthy Republican challenger to President Barack Obama, and leaves America's social conservatives without a clear candidate to throw their support behind.

Huckabee on Saturday night became the latest Republican to opt out of running, declaring that he would stick with his lucrative career as a television and radio personality over a race that promises to be both costly and caustic. By joining Mississippi Gov. Haley Barbour, South Dakota Sen. John Thune and Indiana Rep. Mike Pence on the sidelines, the former Arkansas governor underlined 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 insisted that he could have captured the Republican 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, the winner of the 2008 Iowa caucuses, said on his Fox News Channel show.

The announcement makes an already wide-open Republican field even more unpredictable.

Huckabee is a prominent conservative who would have been a serious contender for the party nod with instant support among Christian evangelicals who dominate the Iowa caucuses and the early South Carolina primary. And with him out of the race, there is no clear candidate out there to for them to rally around.

Onetime 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 Gov. 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. Donald Trump? Highly unlikely.

With so many social conservatives looking for a home, the void could prompt 2008 vice presidential candidate Sarah Palin or Minnesota Rep. Michele Bachmann to get in the race. Palin has yet to say if she will run, while Bachmann is inching toward a bid. Several other possible candidates, including Indiana Gov. Mitch Daniels, are in waiting mode.

The lack of a clear Republican frontrunner reflects Obama's perceived strength as a candidate less than a year-and-a-half before the election. Despite uneven economic growth and continued sluggishness in the employment market, Obama will have the advantage of being an incumbent president with a seemingly unmatchable capacity to generate cash for his campaign. And while events could change dramatically between now and the presidential vote, polls show Obama in a stronger position now than he was before the mission that killed al-Qaida leader Osama bin Laden.

Republican candidates were quick to praise Huckabee after his announcement, making obvious plays for his backers.

"Had Gov. Huckabee decided to run, there is no question he would have been a frontrunner in the 2012 campaign for president," Gingrich said. He said Huckabee "will remain a major force for conservatism and he will play a major role in shaping America's future."

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 said the past few months have been times of deep personal reflection, even as he noted that he was leading some national polls. He painted the decision as a spiritual one.

"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."

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, Huckabee 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.

The former governor said that 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."