Let me raise a red flag about the "red and blue states," which is the reigning theory of U.S. politics. All those blue states (heavily urban and mainly on the East and West coasts) voted for Al Gore. The red states (more rural, Southern and Western) voted for George Bush. Presto, the map defines us. We're a country geographically "polarized" by values and lifestyles. This is a masterful explanation for the increasing nastiness of politics, with only one big drawback. It's wrong.

No one denies that the nastiness is real. It stems partly from the unfolding presidential campaign, the spreading doubt about Iraq and the intense personal contempt many feel for President Bush. But the nastiness preceded these causes -- it existed all through the Clinton years -- and almost certainly will survive them. Why?

If the country were more polarized, you'd expect to find it in the polls. You don't. After scouring surveys, sociologist Paul DiMaggio of Princeton University concluded that "the public actually has become more unified in attitudes toward race, gender and crime since the 1970s." One standard poll item asks respondents to react to this statement: "I don't have much in common with people of other races." In 1987, 23 percent agreed; by 2002, only 15 percent did. Of course, strong disagreements (on abortion, for instance) remain. But these disguise large areas of consensus; 80 percent or more of Americans regularly support environmental regulation.

What's even more absurd is the idea that regions have -- after jet travel, interstate highways, air conditioning, TV and mass migration -- become more different. Texas and New York have more in common now than in 1950 or 1960.

Perhaps party programs have diverged? Not so. On many issues, the parties broadly agree. In practice, both favor bigger government and lower taxes (and aren't embarrassed by the contradiction). President Bush pushed through the Medicare drug benefit, the largest new entitlement since 1965. John Kerry supports most of Bush's tax cuts -- except those for taxpayers with incomes exceeding $200,000. Both parties favor environmentalism, precisely because support is widespread. Both parties ignore the looming budget costs of retiring baby boomers.

To be sure, differences exist, but they often involve critical details, not grand philosophy.

The red and blue states make a pretty graphic. But in 19 states, the victor in the 2000 presidential election won with about 51 percent of the vote or less; small shifts would have reversed the outcomes. Then the graphic and its message -- geographic polarization -- would be ruined.

What's actually happened is that politics, and not the country, has become more polarized. By politics, I mean elected officials, party activists, advocates, highly engaged voters and commentators (TV talking heads, pundits). In his search for polarization, sociologist DiMaggio examined many subgroups by age, race, sex and education. None exhibited more polarization, with one exception: people who identified as "strong" Republicans or Democrats. That's about 30 percent of adults.

Similarly, members of Congress are more polarized: Democrats are more liberal, Republicans are more conservative and "moderates" are scarcer. Political scientist Gary Jacobson of the University of California at San Diego says that members of Congress have "moved further apart [ideologically] than . . . at any time since before World War I."

Congressional polarization has many causes. Republican advances in the South pulled the party from its moderate Northeastern tradition. In the 1950s, 37 percent of House Republicans came from the Northeast, reports Jacobson; now 17 percent do. For Democrats, the opposite has occurred. Fewer conservative Southerners make the party more liberal. Meanwhile, redistricting by both parties has created ever-safer seats. In 1992, Jacobson estimates, 281 House seats were safe; by 2002, the number was 356. Candidates appeal less to centrist voters. In Congress, both parties have adopted confrontational tactics.

The result is a growing disconnect between politics -- and political commentary -- and ordinary life. Politics is increasingly a world unto itself, inhabited by people convinced of their own moral superiority: conspicuously, the religious right among Republicans; and upscale liberal elites among Democrats. Their agendas are hard to enact because they're minority agendas. So politicians instinctively focus on delivering psychic benefits. Each side strives to make its political "base" feel good about itself. People should be confirmed in their moral superiority.

Polarization and nastiness are not side effects. They are the game. You feel good about yourself because the other side is so fanatical, misguided, corrupt and dishonest. Because real differences between party programs have narrowed, remaining differences are exaggerated. Drab policy debates become sensational showdowns -- one side or the other is "destroying" the schools, the environment or the economy. Every investigation aims to expose the other side's depravity: One side's Whitewater becomes the other's Halliburton.

Entertainment and politics merge, because both strive to satisfy psychic needs. Rush Limbaugh and Michael Moore are more powerful political figures than most senators, because they provide more moral reinforcement. Politicians, pundits and talking heads all heed the same logic: By appealing to their supporters' strongest passions and prejudices, they elevate their standing. Of course, much of this is essential to legitimate debate. But it's also a marketing strategy and a formula for power. Stridency sells, because, for many, polarization feels good.

Politics should reflect and, at its best, conciliate the nation's differences. Increasingly, it does the opposite. It distorts, amplifies and inflames conflicts. It's a turnoff to vast numbers of centrist voters who do not see the world in such uncompromising absolutes. This may be the real polarization: between the true believers on both sides and everyone else.