* Republican Huckabee keeps supporters waiting on 2012
* Claims he hasn't made up his mind about running
* Huckabee has advantages, but some signs against a run
* Strong support among religious and social conservatives
By John Whitesides
WASHINGTON, April 18 (Reuters) - Republican Mike Huckabee is riding high in the polls, but he could be running out of time to make up his mind on a run for his party's 2012 U.S. presidential nomination.
With the slow-starting race for the right to challenge President Barack Obama gaining candidates and picking up steam, a few of Huckabee's former advisers have jumped ship to other contenders and some observers see signs he will not run.
In the absence of a decision, one of Huckabee's most ardent supporters in Iowa has even started a phone and e-mail drive to contact other backers of Huckabee's failed 2008 bid and urge them to "Stay Stuck on Huck."
"Nobody knows what he's going to decide," said Randy Davis of Ottumwa, Iowa, who has reached about 500 Huckabee supporters in the state and found only "one or two" not willing to wait. "I've just tried to encourage everyone to be patient."
Huckabee, the former governor of Arkansas, is in no hurry to end the uncertainty. He says he will wait until summer to make a decision and sees no reason to rush into an expensive national campaign.
In an interview last month with a radio talk show host, he ridiculed pundits who were quick to declare he is unlikely to run. "How do you know that? Because I don't know that yet," he said, adding he is "very much" still considering a candidacy.
Ambivalence can be a deadly trait for a presidential contender, but Huckabee would bring many advantages to a 2012 Republican race with no dominant frontrunner.
He won the first nominating contest of 2008 in Iowa and was the last challenger standing against eventual Republican nominee John McCain, building a strong support base among religious and social conservatives who dominate some early Republican contests.
'POSITIVE INTENSITY' AMONG SUPPORTERS
He leads many public opinion polls of the Republican presidential field, and holds a significant edge over his rivals in the Gallup Poll's "positive intensity" measure of depth of support.
But unlike Republican rival Mitt Romney, another losing candidate in 2008 who has long been planning another campaign, Huckabee has not been lining up staff or keeping his donors and supporters in line.
His two top Iowa operatives in the 2008 campaign have moved to other candidates, and his campaign manager shifted to a congressional staff job.
Other candidates for the role of conservative favorite have emerged as the Tea Party movement gained prominence with its agenda of reduced spending and limited government.
U.S. Representative Michele Bachmann and former Senator Rick Santorum are pushing hard in Iowa, which kicks off the nominating battle in February, for the state's sizable base of evangelicals, abortion rights opponents and Tea Party backers.
With Republicans facing a tough race against a sitting president in an improving economy, Huckabee might decide it is smarter to stay on his lucrative Fox News Channel show and make another run in 2016 when the White House will be vacant.
"If he entered the race and didn't do well he would lose all credibility" as a conservative leader, said Steffen Schmidt, a political scientist at Iowa State University. "He's sending out a lot of signs that he's not going to do it."
Two prominent Republicans, Romney and former Minnesota Governor Tim Pawlenty, have jumped in the race by forming exploratory committees to begin raising money.
Huckabee's decision to wait until summer could create problems in Iowa, where organization is crucial because of the state's unique caucus system requiring voters to attend an evening community gathering and make a public show of support.
The Iowa straw poll in August is an early test of that organizing strength. It was Huckabee's second-place finish to Romney there in 2008 that solidified his support among social conservatives and started his momentum.
"Those people who are skillful at managing the Iowa caucuses aren't going to wait until mid-summer to find a candidate," said Schmidt. "I don't think he can wait very long, honestly, I think he has to make a decision soon."
Meanwhile, Davis is keeping hope alive for Huckabee supporters and waiting for a sign.
"We just have our fingers crossed that he will run," he said. "If he doesn't people will say this was a waste of time, but I think it's worth the risk." (Editing by Todd Eastham)