WASHINGTON — It was a jarring moment from an ordinarily smooth pol. Haley Barbour, governor of Mississippi, chairman of the Republican Governors Association and 2012 presidential prospect — which helped explain the big turnout at a breakfast Wednesday sponsored by the Christian Science Monitor — was asked why so many people seem to believe that President Obama is Muslim.

“I don’t know why people think what they think,” Barbour said. Fair enough. But then out came this odd statement: “This is a president that we know less about than any other president in history.”

Really? Less than Benjamin Harrison? Franklin Pierce? By the time he launched his candidacy, Obama had written an autobiography and a second, more policy-oriented book threaded through with examples from his personal experience — though Barbour said he hasn’t read these. What is it, exactly, that we don’t know about him?

After the formal session had concluded, Barbour elaborated on what he meant. “There is not much known about his time in college or growing up,” he said. Actually, governor, Obama has revealed a lot more than George W. Bush was willing to say about what he did when he was young and irresponsible. In “Dreams from My Father,” Obama discussed his drug use in high school and college — “Pot had helped, and booze; maybe a little blow when you could afford it” — and his friendships with Marxist professors.

Barbour, continuing, “We don’t know if he chopped down a cherry tree.” Uh, you might want to double-check on that tree thing.

“We don’t know any of the childhood things we know about Ronald Reagan. I don’t say it as an insult or as anything other than an observation. Somebody asked, ‘Why would people question things?’ We just don’t know him.”

During the breakfast, Barbour made clear that he did not subscribe to this wackadoodle view. “I accept just totally at face value that he is a Christian,” Barbour said. “He’s said so throughout the time he has been in public life. That’s good enough for me.”

But was Barbour trying, none-too-subtly, to fan the flames of Obama-as-Muslim-Manchurian-candidate conspiracy theorists? I doubt it. A big piece of Barbour’s message was that the best way to run against Obama and the Democrats was head-on — on the economy, taxes and debt. Social issues and closet Muslims are so much distracting noise, as Barbour sees it.

I don’t pretend to understand the mass delusion about Obama’s religion, most prevalent among members of Barbour’s party, but I suspect there is something significant in Barbour’s characterization of Obama as an unknown quantity. Except I would translate it this way: This discomfort, among a disturbing segment of Americans, is not that Obama is unknown as much as that he is unfamiliar. It’s not that, as Barbour put it, those who question Obama’s religion “just don’t know him” — it’s that they don’t know anyone like him.

Barbour pointed to the fact of Obama’s brief tenure in public life, but this cannot be the real explanation. At another point in the session, Barbour was describing the potential advantages of non-career politicians such as his nominee for governor of California, former eBay chairman Meg Whitman. She’s not exactly a household name, but no one’s whispering that Whitman has a secret religion.

This unfamiliarity mattered less to people when Obama was the anti-Bush than it does, perhaps, when he is the actual president presiding over an actual economy. That may help explain why the number of people who believe he is Muslim has grown since the election. Anxiety is the mother of conspiracy theories, and there is more than enough anxiety to go around right now.

As for Barbour — maybe he could try reading one of the books by the man he might end up running against?