When it comes to the issue of immigration, the American people are evenly divided. As a March 28 Public Opinion Strategies poll found, 39 percent of Americans think immigration is an economic benefit and 40 percent think it is an economic threat. Republicans are more likely than Democrats to see immigration -- and immigrants -- as a danger, but not by much. A separate Quinnipiac poll this month found that 51 percent of Democrats see illegal immigration as a "serious problem," compared with 67 percent of Republicans.

Though I have not seen the numbers broken down this way, I am convinced that the real dividing line on immigration is not party affiliation or political ideology but class. Working-class Americans, who find their factory wages or their service sector jobs undercut by new arrivals to the country, see a problem. White-collar Americans, who benefit from the illegal immigrants who accept minimum wages to build their houses, clean their cars and wash their dishes, see immigration as a boon.

In a rational democracy, this class divide would be front and center in the debate over what to do about the 12 million undocumented immigrants who live in this country. Instead, we get Rep. Tom Tancredo, a soft-spoken demogogue from Colorado who chairs the House Immigration Reform Caucus.

Tancredo's main concern about illegal immigration is not economic. He worries about the threat undocumented Hispanics pose to the cultural purity of the United States. As he explained to me last year, "You have to understand there is a bigger issue here. Who are we? Do we have an understanding of what it means to be an American, even if we are Hispanic or Italian or Jewish or black or white or Hungarian by ancestry? Is there something we can all hang on to? Are there things that will bind us together as Americans?"

The congressman from Colorado speaks about the "cult of multiculturalism." He believes Hispanic immigrants no longer feel the need to assimilate into American culture. "You have, at least, divided loyalties," he explained.

Tancredo, who has become a constant presence on cable news and is a Page One profile subject in today's Washington Post, relies heavily on the ideas of Harvard's Samuel P. Huntington, an alarmist scholar who recently wrote a book called "Who Are We?: The Challenges to America's National Identity."

Huntington's thesis: "In this new era, the single most immediate and most serious challenge to America's traditional identity comes from the immense and continuing immigration from Latin America, especially from Mexico, and the fertility rates of these immigrants compared to black and white American natives."

These ideas have very little to do with economic concerns about immigration's effect on wages, or the hardships that undocumented workers face. In fact, Huntington and Tancredo are calling for a radical reimagining of America. No longer supporting the great melting pot experiment of Walt Whitman, they would like to freeze this nation in time, defining it forever as an 18th century Anglo-Protestant colony.

Let us hope that America's voters -- and their elected representatives in Congress -- are smart enough to see the difference.