I’m honestly shocked. He was the one guy among the fencesitters who I thought was a lock to jump in, especially if Huckabee sat out and created a vacuum for a southern candidate. He made high-profile appearances recently in Iowa and New Hampshire and had plans for more trips in the coming weeks. A new interview with him about the possibility of running appeared just 24 hours ago at Newsweek.

What happened?

“I will not be a candidate for president next year. This has been a difficult, personal decision, and I am very grateful to my family for their total support of my going forward, had that been what I decided.

“Hundreds of people have encouraged me to run and offered both to give and raise money for a presidential campaign. Many volunteers have organized events in support of my pursuing the race. Some have dedicated virtually full time to setting up preliminary organizations in critical, early states and to helping plan what has been several months of intensive activity.

“I greatly appreciate each and every one of them and all their outstanding efforts. If I have disappointed any of them in this decision, I sincerely regret it.

“A candidate for president today is embracing a ten-year commitment to an all-consuming effort, to the virtual exclusion of all else. His (or her) supporters expect and deserve no less than absolute fire in the belly from their candidate. I cannot offer that with certainty, and total certainty is required.

“This decision means I will continue my job as Governor Mississippi, my role in the Republican Governors Association and my efforts to elect a new Republican president in 2012, as the stakes for the nation require that effort to be successful.”

Verrry curious. Barbour’s worked tirelessly for the RNC, RGA, and other conservative groups for years; his fundraising ability is legendary. I can’t believe the fire wouldn’t be there if he thought he had a path to victory. But even with his southern advantage, maybe he didn’t: He’s not a natural match for either Iowa or New Hampshire and it’d be tough to hold South Carolina having lost all of the earlier primaries. Could be that he looked at the map and thought it was a lost cause. Or, given what he said about this being a “difficult, personal decision,” maybe he bowed to family pressure. His wife famously told the AP a few weeks ago that the thought of a campaign “horrifies” her because it would be “a huge sacrifice for a family to make.”

Or maybe this is the answer:

[Mitch] Daniels is candid: He’d be less inclined to launch a White House bid if Barbour does the same.

“My first inclination would be to help Haley,” said Daniels, adding: “It would be unusual [if we both ran]. On every past occasion, we’ve been teammates.”

There’s a new story at WaPo this morning about the Daniels’s presidential Hamlet act in which he describes his thinking at this point as “muddled.” Barbour dropping out will help clarify things a bit since, if Daniels does run, he’s now practically guaranteed Barbour’s endorsement and fundraising help. Barbour might not make it to the White House on his own, but if he joins forces with Mitch the Knife, he could get there as VP, chief of staff, or in any number of other roles. He’s a bottom-line kind of guy, and that’d be a shrewd bottom-line calculation. Now all Daniels has to do is play ball.

Update: Chris Cillizza notes an AP story published yesterday that claimed Barbour was “expected to join the field as early as this coming week.”

Update: Idle thought: Are we now guaranteed a Huckabee candidacy? It’s hard to imagine a GOP primary with no southerners in the mix.

Update: Yes, technically Gingrich is a “southern” candidate, but he’s not southern-identified the way Huck and Barbour are. And it’s an open question at the moment whether major players in his own home state will line up behind him.

Update: A source close to Daniels tells NYT reporter John Harwood he’s leaning towards yes: “mitchdaniels confidant: Indiana Gov. now ’60 to 70%’ likely to seek 2012 GOP nomination”.