Apparently psychology tells a lot about why Kerry is winning.

In many situations, social decision-making isn't a bad idea at all. After all, the world is a complicated place, and other people often do have information that we lack. So, we can often do reasonably well, or at least no worse than the people we are copying, by letting them do the hard work for us.

But sometimes the people we are copying aren't working either, and that's where the problems come in. When everyone is looking to someone else for an opinion—trying, for example, to pick the Democratic candidate they think everyone else will pick—it's possible that whatever information other people might have gets lost, and instead we get a cascade of imitation that, like a stampeding herd, can start for no apparent reason and subsequently go in any direction with equal likelihood. Stock market bubbles and cultural fads are the examples that most people associate with cascades, because they are generally accepted to represent "irrational" behavior (although, curiously, not to the people who are participating in them—just ask a teenager why she wants to get her navel pierced; she won't say "because it's a fad"), but the same dynamics can show up even in the serious business of Democratic primaries.

For example, when New Yorkers go to vote next Tuesday, they cannot help but be influenced by Kerry's victories in Wisconsin last week. Surely those Wisconsinites knew something, and if so many of them voted for Kerry, then he must be a decent candidate. But the voters in Wisconsin were just as influenced by the decisions of voters from the previous round of primaries, who were in turn influenced by the round before theirs, and so on. Before any given primary, if all previous votes have resulted in an even split among candidates, then the prospect for independent thinking still exists. But as the sequence of primaries progresses, the likelihood of successive even splits rapidly diminishes, and one candidate inevitably starts to look like a winner. At that moment, the cascade starts, and all subsequent votes then become exercises in rubber stamping. The reason why this year is so striking is that because Iowa and New Hampshire voted the same way, the onset of the cascade was immediate. And the result is that less than 1 percent of all voters effectively decided that Kerry was to be the Democratic nominee—the rest of us are just tagging along.

Not surprisingly, many people (pundits especially) are reluctant to concede this point. We think of ourselves as autonomous individuals, each driven by own internal abilities and desires and therefore solely responsible for our own behavior, particularly when it comes to voting. No voter ever admits—even to herself—that she chose Kerry because he won New Hampshire. To acknowledge that our decisions might not, in fact, be ours at all, but instead might be a reflection of what we think everyone else thinks diminishes our sense of individuality. That's why we prefer to invoke other explanations for why we did whatever we did—Kerry supporters might talk about his "electability," but they believe the support for him has some other basis, such as foreign-policy experience, than just following the crowd. Even Asch's unwitting subjects—clear victims of manipulation—when interviewed afterwards gave other rationalizations for their decisions, some of them succumbing to what Asch called a "distortion of perception" in which they perceived the majority as being correct.