In this case, it took only hours. The forgery claim appeared to have first started as an offbeat blog post from an Atlanta-based art director at an ad firm, Bryan Michael Nixon, less than two hours after Obama's statement. By the end of the day it had become a headline on Drudge Report, one of the single most trafficked news sites on the internet. The debunked forgery revelation drew thousands of comments on messageboards, migrated to birther and truther conspiracy guru Alex Jones' site, while a video explanation was viewed over 160,000 times on YouTube.
The basis for the forgery claim lay in a basic misunderstanding of how computer image formats work. Nixon observed in his post that the PDF file of Obama's long form birth certificate could be broken down into "layers," including a background and separate foreground text. "This in no way proves that anything on it is fake, but only that the document from the WH was composed of multiple elements," he wrote. "How to interpret it is up to the viewer."
Of course, viewers who didn't let President Obama's short form birth certificate derail their birther fantasies back in 2008 interpreted it exactly as you'd expect, spreading the "layering" claim on sites like conservative messageboard FreeRepublic as proof it was faked.
In fact, the effect was not a sign of foul play at all, but a common attribute of PDF files containing text as an image. On many PDFs, a feature called OCR (optical character recognition) recognizes the letters in the image and separates them into their own layer. This explains why you're able to highlight and copy raw text from some PDF files even though it's actually not a word processing document.
The conservative news site National Review Online received so many e-mails from their readers on the "layer" theory that they looked into it and issued their own thorough debunking. To demonstrate that the long form release was nothing unusual, NRO scanned a copy of their own magazine cover into a PDF file, easily recreating the same layer effect in Adobe Illustrator.
As TPM has documented, birthers have wasted no time in promoting alternate theories undermining the president's legitimacy since the release of the long form birth certificate.