MSNBC has just conducted a poll in which it asked people if they thought opinion polls accurately reflected actual opinions. The network informs us that 88 percent of those polled answered "no."

This sounds like a surreal joke, but then stories about contemporary politics often do. There is no polite way to phrase this: When it comes to politics, the average person is an idiot. Depressing evidence for this claim can be found in a recent New Yorker essay by Louis Menand, which surveys the political-science literature regarding why people vote the way they do.

The conclusions from this literature include:

— No more than 10 percent of the population can be said to have a coherent political belief system, using even a loose definition of that term. Most people's political beliefs, to the extent they have any at all, suffer from a lack of what political scientists call "constraint" — i.e., little or no logical connection exists between the positions they hold. For example, a large proportion of voters see no contradiction between being in favor of both lower taxes and increased government services.

— Perhaps a quarter of all voters vote on the basis of factors that have no "issue content" whatever. They vote for candidates who seem likable, or optimistic, or for those whose campaign posters are particularly eye-catching. According to Princeton political scientists Christopher Achen and Larry Bartels, millions of voters in the 2000 presidential election based their votes on what the weather had been like lately.

— Voters are remarkably bad at calculating their own self-interest, even when their self-interest and their political beliefs coincide. Bartels gives the following example. Only the richest 2 percent of Americans pay estate taxes. Yet among people who believe that the rich ought to pay more taxes, and who also believe that growing income inequality is a bad thing, two-thirds also favor repeal of the estate tax. Menand observes that this sort of data helps explain the otherwise puzzling fact "that the world's greatest democracy has an electorate that continually 'chooses' to transfer more and more wealth to a smaller and smaller fraction of itself."

Even if we ignore how many people have no coherent political beliefs, or base their voting on irrational factors, the sheer ignorance of the average American should take us aback. Seventy percent of Americans can't identify their senators or their congressman. Around 30 million can't find the United States on a map.

Now consider that the upcoming presidential election will almost certainly be decided by voters who have not yet decided for whom they are going to vote (in 2000, 18 percent of voters made their decision in the final two weeks of the campaign, and 5 percent — far more than the decisive margin — made their decision on Election Day itself). It's safe to say that almost everyone who has been paying the slightest bit of attention to national politics, and who has anything resembling coherent political beliefs, has already decided what he or she is going to do on Nov. 2, at least in regard to the presidential election.

But the cold fact is that tens of millions of Americans don't fit that description. They normally pay no attention to politics; whatever political beliefs they do have tend to be wildly inconsistent; and they base their votes on frankly irrational factors.

These are the crucial swing voters in the crucial swing states, who will decide who should occupy the world's most powerful political office for the next four years.

There is, of course, no reason to doubt that democracy "works." Anyway, we are assured that it does by our elected leaders — and if you can't trust them, who can you trust?

Paul Campos is a law professor at the University of Colorado and can be reached at