By Eric Etheridge The New York Times

“Slowly but surely, this is going mainstream,” says Allpundit.

“Did Lou Dobbs really GO THERE? Seriously? This is getting absurd,” says the First Read team at MSNBC.

Six months into his presidency, the charge that Barack Obama is — literally — un-American is gaining, not losing, steam. Yes, the Birther bump is growing.

Need some backstory? Allow The Atlantic’s Marc Ambinder to explain:

“Birthers, for the uninitiated, is a term used by the media to ridicule those who believe that the president’s Hawaiian birth certificate is fake and that because he was ostensibly born in Kenya, not the United States, he was never eligible to be president in the first place.”

To the extent that one can conclusively prove such things in our postmodern age, this claim has been extremely thoroughly debunked.

The birther movement may be premised on a fictional belief, but it is savvy: Birthers now wear the term “birther” as badge of honor, as if they were a persecuted minority — which, come to think of it, is one mechanism for solidarity in the face of evidence to the contrary.

Whether the idea has been debunked or or not is not something that seems to impact the birther movement. In fact, as Dave Weigel points out, “the ‘birther’ movement began in response to Obama’s own efforts to debunk rumors.”

One year ago this week, the presidential campaign of then-Sen. Obama launched FightTheSmears.com, a Web site designed to push back against false rumors about the first African-American presidential nominee.

To push back against rumors that he was not born in Hawaii, the campaign reproduced a Certificate of Live Birth from the state’s Health Department.

Instead of terminating the conspiracy theories, that inspired new theories — that the certificate had been forged or that even if it hadn’t been forged it was the sort of certificate that could be given to someone born outside of the United States.

But the certificate is specific about Obama’s birth in Honolulu, down to the 7:24 p.m. time.

Weigel, whose Washington Independent article provides a detailed history of the movement, says “the cottage industry of conspiracy theories about the president’s birth shows no signs of disappearing,” even despite suffering “scores of embarrassing legal defeats, and even after tussles between the attorneys who’ve turned frivolous lawsuits about the president’s citizenship into full-time jobs.”

The theories have found a home in talk radio and on conservative Web sites such as Free Republic and WorldNetDaily.

Conspiracy theorists are increasingly sending letters to their local papers, embarrassing members of Congress at town hall meetings, and hounding Capitol Hill staffers about challenges to the president’s citizenship.

Back at The Atlantic, Ambinder provides his list of “the most prominent birthers”:

Alan Keyes, the former presidential candidate and Obama Senate challenger; Orly Tait, a wonderfully named lawyer from California; Phil Berg, a Democrat; and Michael Reagan, son of Ronald Reagan, and a prominent radio talk show host.

This is, at once, a fringe movement and something greater. It’s fringe because no important Republicans believe it, and most are offended by it. It’s greater because some fairly prominent local lawmakers are beginning to sign birther petitions.

No list of prominent anythings that begins with Keyes can be considered a murderer’s row, but lately some of the first-string have been flirting with the idea.

As the First Readers noticed and as James Rainey recounted in The Los Angeles Times two weeks ago, Lou Dobbs fielded a call from a birther — “David from Freeport, N.Y.,” — who was “musing darkly about President Obama ‘rushing all these programs through by whatever means,’ knowing he will soon be exposed as a fake, a fraud, a … Kenyan.”

“Certainly your view can’t be discounted,” Dobbs replied.

On July 20, Rush Limbaugh went further: “Barack Obama has yet to have to prove he’s a citizen. All he’d have to do is show a birth certificate.”

On July 21 on Larry King, Liz Cheney passed up several chances to “denounce the birthers,” writes Joan Walsh in Salon.

Instead, “Cheney demurred, telling King the Birther movement exists because “people are uncomfortable with a president who is reluctant to defend the nation overseas.’ “

Also on his show, King played the viral video that is partly responsible for fueling the current boomlet. In it, a birther challenges Rep. Mike Castle, a Delaware Republican, at a town-hall meeting that took place earlier this month.

“What’s most notable, to me, at least,” says Ambinder, “is not how scared Castle looked or how passionately the woman argued for Barack Obama’s foreign birth. It was the reaction of the audience, a good portion of which erupted into cheers and youbetchas.”

“The real story in all of this,” say MSNBC’s First Readers: “is that Republican Party has a HUGE problem with its base right now.”

That some Republicans believe a man who won last year’s presidential contest by seven percentage points is not the legitimate president is a base problem much bigger than Cindy Sheehan anti-war protesters or black helicopter conspiracy theorists who flock to some Ron Paul events.

Check out how flummoxed Castle looked. How many other Republican elected officials are dealing with questioners like this woman?

Another way to put that last question is: How many Republican officials are dealing with questioners like this woman who are members of Congress?

The answer seems to be at least 10, since that’s the number of GOP representatives who have signed on to sponsor a bill that calls for future presidential candidates to provide a birth certificate.