James Bow explains why Dean's support, though it seemed enormous if you looked at one chunk of the Internet, was thin on the ground in Iowa, in the Actual Real World of live human voters. He uses what became (after 'Headless Body Found in Topless Bar,' maybe) the most famous headline ever run in a daily newspaper:
"Opinion poll after opinion poll showed Dewey with a substantial lead, right up to the day before the election. So certain of the results that the managers of the strike-riddled Chicago Daily Tribune had the inexperienced print-setters set out the headline DEWEY DEFEATS TRUMAN and sent everybody home early, much to their later embarrassment because, of course, Truman defied all expectations and won handily.
"It was a shock. The pollsters hadn't anticipated this at all, and they had all of the latest technology at their fingertips. They'd used the telephone, and America's burgeoning telephone network to reach thousands of Americans and gather their opinions. ... So why didn't it work?
Turns out, it was the technology that was the pollsters' downfall, because although many Americans had telephones, many Americans did not. Those that did not own phones tended to be poor, rural, and disproportionately open to Truman's New Deal message, which he continued to aggressively campaign on, state-to-state, town-to-town and person-to-person. ...
"Humans can't picture how big the world is, and sometimes they think that if they're speaking to an active community of hundreds (which describes the blogosphere to a 'T'), they have the ear of the world, or at least the part of the world that matters. Sometimes, in that amplified setting, our discussions and our opinions get pulled off of what's seen as conventional wisdom in the offline world. And sometimes, when reality snaps back at us, we are shocked.
The whole thing is worth a read.