NO issue divides economists and mere Muggles more than the debate over globalization and international trade. Where the high priests of the dismal science see opportunity through the magic of the market’s invisible hand, Joe Sixpack sees a threat to his livelihood. This gap in perspective grows especially wide whenever the economy experiences short-run difficulties, as it is now. By all indications, the issue could come to dominate the presidential campaign.

Economists are, overwhelmingly, free traders. A 2006 poll of Ph.D. members of the American Economic Association found that 87.5 percent agreed that “the U.S. should eliminate remaining tariffs and other barriers to trade.”

The benefits from an open world trading system are standard fare in introductory economics courses. In my freshman course at Harvard, we start studying the topic in the second week, and we return to issues of globalization throughout the year. The basic lessons can be traced back to Adam Smith of the 18th century and David Ricardo of the 19th century: Trade between two countries creates winners and losers, but it leaves both nations with greater overall prosperity.

The general public, however, is less likely to take its cue from Adam Smith than from Lou Dobbs. In December, an NBC News/Wall Street Journal poll asked Americans, “Do you think the fact that the American economy has become increasingly global is good because it has opened up new markets for American products and resulted in more jobs, or bad because it has subjected American companies and employees to unfair competition and cheap labor?”