Just how many people attended Saturday's 9/12 tea-party protest? Estimates by conservatives range from the hundreds of thousands to the millions -- numbers they say indicate a growing anti-Obama grassroots movement. Unsurprisingly, liberal pundits are pushing back, saying protesters came out in the tens of thousands. So far, the debate is hinging on photos of the rally, which appear to show the National Mall packed from the Capitol to the Washington Monument, 16 blocks away. A National Park Service map pegged to the 2008 inauguration appears to show that the Mall holds about a million people. Bloggers have overlaid the map with photos from Saturday. Case closed, right? Not so, as there's an important detail both conservatives and liberals are ignoring.

What no one has noted is that two-thirds of the National Mall was filled by an entirely separate event on Saturday that had nothing to do with protesting the president. September 12 just happened to be the 24th-annual Black Family Reunion, which ran from 7th Street all the way to the Washington Monument. I spent several hours on the Mall on Saturday, and there's no question that protesters numbered at least in the tens of thousands, but they were isolated to only a fraction of the area they're credited with having filled. The Black Family Reunion, a peaceful and friendly event designed around "healing and uplifting black families," featured mild-mannered African American families meandering through a series of promotional tables and large white tents scattered across the Mall. One crowd gathered across from the Washington Monument, not to protest health-care reform but to enjoy a Christian-themed R&B concert, where volunteers handed out free water bottles and bananas.

Not even the most biased observer could have mistaken these people for anti-Obama protesters. So why did so many pundits conflate the cheery Black Family Reunion with the angry tea-party protesters? The answer, I think, is that they either weren't there or didn't bother to leave the protest's zenith on the Capitol steps. It's an institutional hazard of covering protests that reporters seek out the center of the action and don't budge, giving them great anecdotes from individual attendees but little sense of the event's overall scope. Similarly, it's easy for bloggers to just read after-action reports or browse a few photos before drawing conclusions. But these are both risky strategies for covering big events, and it's easy to see why people are so confused about Saturday's attendance figures.