A naive person might believe that Barack Hussein Obama was born, as he has long said he was, in Hawaii to a young American mother and a distant father from Kenya. There are notices in two local papers and the certification of birth is filed in the state of Hawaii’s records.

An independent body — FactCheck.org — part of the Annenberg Public Policy Center at the University of Pennsylvania, asked to see a copy of the original during last year’s campaign. FactCheck is non-partisan and takes all sorts of politicians’ claims to task. Here’s its take on Obama’s birth certificate: “FactCheck.org staffers have now seen, touched, examined and photographed the original birth certificate. We conclude that it meets all of the requirements from the State Department for proving US citizenship. Claims that the document lacks a raised seal or a signature are false. . . Our conclusion: Obama was born in the USA just as he has always said.”

You may be persuaded. Once I’d seen the short-form certificate online, verified by independent journalists and vouched for by state authorities, I was, too. But staggering numbers of Americans remain sceptical. In fact, a majority of Republican voters — 58% — either do not believe or are unsure that Obama is a natural-born American citizen. That means most Republicans believe Obama is constitutionally illegitimate in the presidency because the constitution reserves it for those born in America. The scepticism is — surprise! — concentrated in the south. In Virginia, a southern state that backed Obama last year, only 53% are sure Obama is legitimately president and 70% of Virginia Republicans either don’t believe he is an American or aren’t sure. A poll last week also found that many Republicans believe this issue has not received enough media attention.

What do they believe? The most common theory is that Obama was born in Kenya while his mother was visiting his father. The Hawaiian birth certificate exists, the sceptics claim, because Hawaii recognises as natural-born citizens those born to American mothers temporarily outside the United States. The only problem with that theory is the certificate would mention that fact and it doesn’t.

So Obama was born where all the evidence says he was: Honolulu. Why would a woman in her last month of pregnancy travel halfway around the world to deliver a child in a developing country and then bring him back home, even though he wouldn’t have had a passport? How would she get him into the United States unless someone at the border was in cahoots? “You couldn’t sell this script in Hollywood,” Robert Gibbs, the White House press secretary, told reporters last week.

Why does this story stay alive? Some, like me, didn’t understand the Hawaiian intricacies at first: we thought there was a single long-form certificate that could resolve the question. But, as FactCheck notes: “The Hawaii Department of Health’s birth record request form does not give the option to request a photocopy of your long-form birth certificate, but their short form has enough information to be acceptable to the State Department.” So Obama did all he could to make this go away.

Yet the conspiracists have only become more adamant. A slew of radio show hosts have fixated on the question; Lou Dobbs, CNN’s resident crank, broadcast several segments expressing doubt about Obama’s birthplace. Sean Hannity, a Fox News pundit, ran two reports on a soldier who refused to follow orders from Obama because he doubted his eligibility to be president. When Major Stefan Cook’s orders to deploy to Afghanistan were revoked, he and his lawyer took it as an admission on the part of the military that the president is not, in fact, a legitimate citizen by birth.

On cue, as Obama turned 48 last week, a Kenyan birth certificate popped up on the web. It was immediately exposed as a forgery based on a 1959 Australian birth certificate, but the pressure hasn’t let up. Obama’s legitimacy as president has been challenged in five lawsuits, all dismissed.

WorldNetDaily, the far-right website, has run countless editorials, letter-writing campaigns and billboard advertisements on the question. WND is a fringe web publication — but its fringe has, by some estimates, about 2m visitors a month.

Rush Limbaugh, the mega-chat show host, has raised the issue and Michael Savage, the rabid rightist, has said: “We’re getting ready for the communist takeover of America with a non-citizen at the helm.” Other, calmer Republican activists have denounced the so-called “birthers”. The cannier ones have argued that this issue has been drummed up by Democrats to discredit the Good Old Party (and it has). But it’s hard to accept that explains everything.

The bolder rightwingers have condemned the whole thing: radio star Michael Medved has called the birthers “crazy, nutburger, demagogue, money-hungry, exploitative, irresponsible, filthy conservative imposters”. But leading Republican politicians, aware of how powerful the conspiracy theory is among their supporters, have tried to avoid the issue. The Alabama Senator Richard Shelby, for example, told a town hall meeting last February: “Well, his father was Kenyan and they said he was born in Hawaii but I haven’t seen any birth certificate”, even though a resolution on July 27 — issued on the 50th anniversary of Hawaii’s statehood — declared Obama a citizen unanimously (with some Republican abstentions).

This is the silly season. But this silly story seems to me an indication of something more ominous. The demographics tell the basic story: a black man is president and a large majority of white southerners cannot accept that, even in 2009. They grasp conspiracy theories to wish Obama — and the America he represents — away. Since white southerners comprise an increasing proportion of the 22% of Americans who still describe themselves as Republican, the GOP can neither dismiss the crankery nor move past it. The fringe defines what’s left of the Republican centre.

The chilling implication is that a large number of Americans believe the president has no right to be in office and has fraudulently manoeuvred himself there.

I hope the secret service is on alert. If we thought racial panic had ended with Obama’s election, the resilience of this story in key parts of the country is a helpful wake-up call.

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