The bar was already lowered before the Enquirer stepped over it
There's a bit of misinformation out there about the John Edwards scandal that should be nipped in the bud. I've seen it a number of times now, most recently in David Carr's NYT column:
When The National Enquirer wrote that the former presidential candidate John Edwards had had an affair and had recently met with the woman and a child she recently bore, the mainstream media mostly passed on the story. But the public would not let go. Armed with different standards and megaphones of their own, nontraditional sources pushed on the story all over the Web until it broke...
Let's give credit where it's due. The Enquirer had the details, but the story was being pushed on the Web before the tabloid published anything. As you'll well recall, HuffPo's Sam Stein had the first scoop, which was picked up by (among others) Ted Frank and Mickey Kaus. DKos's Ben Bang pushed back immediately too, which only helped give the story life.
Wikipedia credits Page Six with the very first mention of the affair, in an August 07 blind item.