With a surprise announcement that he lacks "the absolute fire in the belly" to pursue the presidency, Mississippi Gov. Haley Barbour on Monday became the latest prominent Republican to pass up the 2012 nomination contest.

The decision, disclosed in a conference call with about 50 advisers and supporters, reflected Barbour's hard-headed assessment that the odds were against winning, according to advisers. His move shrinks the Republican field in a race that has already lured a smaller than expected field of contenders.

Barbour "choked up" in the midafternoon call, one participant said. In a statement on his official website that cited an absence of wholehearted desire to run, the governor called it "a difficult, personal decision." He also said, and advisers confirmed, that his family had given its "total support" to a presidential run.

A former Washington lobbyist and Republican National Committee chairman, Barbour is one of the most prodigious fundraisers in American politics. In recent months, he made campaign-style visits to early-voting states and lined up staff and contributors.

But the 63-year-old southerner with a syrupy drawl also faced unique obstacles that threatened to distract attention from his campaign message. As he began his campaign, he had to defend comments that suggested a lack of sensitivity about segregationist activities in his home town during the 1950s and about contemporary efforts to honor an early Ku Klux Klan leader with a commemorative license plate tied to the 150th anniversary of the Civil War.

"To beat Obama, it's got to be all about Obama, and it's going to take a Republican who can make it 100% about Obama," said one adviser, requesting anonymity to discuss internal deliberations. Another adviser said that by the time Republicans choose their nominee, Obama will have $400 million to $500 million in the bank, adding a further hurdle to defeating the incumbent.

Barbour had set a late April deadline and began sending signs internally over the last 10 days that he might not run. He had outpatient surgery for lower back pain last Monday, his office announced, after months of political travel aggravated the discomfort. Friends said the medical problem did not play a part in his decision.

Steve Scheffler, a Republican National Committee member in Iowa, said he was "a little surprised" by the announcement. He attended several Barbour appearances in the state this year, including a spaghetti dinner in Tiffin last month, where the governor was "well received."

Barbour's decision, according to Scheffler, leaves the GOP race where it has been for months: "undoubtedly the most wide-open in 50 years."

Barbour had begun setting himself apart from potential rivals by questioning the continued U.S. military deployment in Afghanistan. The former Reagan White House political aide also had said that defense spending should not be exempt from budget cuts.

Mike Dennehy, hired to run his New Hampshire primary campaign, said Barbour "was striking a chord with people as a truth teller," having reached at a stage in his career when "he didn't really have anything to lose, which made him very appealing as a candidate. "

Some of the potential 2012 contenders may be running with an eye toward 2016 and "don't have that freedom," he added, "and it boxes them in."

Last fall's big Republican midterm victory had been expected to draw more candidates into the 2012 competition; instead, a number of high-profile possibilities said they wouldn't run, including New Jersey Gov. Chris Christie and former Florida Gov. Jeb Bush. Others opting out included South Dakota Sen. John Thune and Indiana Rep. Mike Pence.

Several potential contenders have yet to take clear steps to get in, including former Govs. Sarah Palin of Alaska and Mike Huckabee of Arkansas, raising questions about their intentions.

Former Govs. Mitt Romney of Massachusetts and Tim Pawlenty of Minnesota have filed official candidate papers. Former House Speaker Newt Gingrich and former Sen. Rick Santorum have taken steps toward full-fledged runs. Reps. Michele Bachmann of Minnesota and Ron Paul of Texas are also pointing toward presidential campaigns.

Indiana Gov. Mitch Daniels, a close friend of Barbour's, is nearing a decision point. There has been widespread speculation that the two agreed not to compete against each other, a notion that a Barbour adviser described Monday as "ridiculous."

paul.west@latimes.com