Here's a puzzle: All nonadvocacy surveys of public opinion show only tiny minorities - commonly about 10 to 20 percent - favoring increased legal immigration. Last month's national survey by the Pew Center for the People and the Press is typical, reporting only 17 percent in this camp.
Yet the two opposing bills that have been roiling the Senate both include little- scrutinized provisions that would greatly increase permanent legal immigration. These survived quietly, largely ignored by politicians and the press, while emotional debate and commentary focused on illegal immigrants and temporary workers.
How can this be? In a representative democracy, why would political leaderships promote policies on legal immigration that have support from only tiny minorities of those who elect them?
The explanations of this puzzle are actually well-known: First, there is a huge gap between public opinion and elite opinion on immigration issues. The best data come from a biennial survey by the Chicago Council on Foreign Relations, which creatively surveys two distinct samples to allow such comparisons: A "public opinion" sample representative of the entire US population, and a separate sample of 450 "leaders" on foreign policy issues (congressional members and senior staff, executive branch officials, university administrators and professors, journalists, and leaders of corporations, unions, religious organizations, interest groups, etc.).
The Chicago Council summarizes the outcome in a single clear sentence: "Immigration - widely seen as a threat to low-wage American workers and as a possible source of terrorism - draws remarkably stronger reactions from the public than from leaders."
Remarkable indeed. The most recent such comparison, from 2004, shows that 33 percent of the "leaders" group wanted to increase legal immigration, vs. only 11 percent of the public opinion sample. Only 10 percent of the leaders group wanted to decrease the level of legal immigration, while fully 54 percent of the public opinion sample supported such decreases.
Members of the US Senate - an elite among elites - do seem to be quite insulated from the views that pollsters routinely find among broad public opinion. On this issue senators may be even further disconnected from those who elect them as they are also surrounded by flocks of immigration lobbyists representing small but well-organized and heavily financed interest groups.
These interest groups are regional, economic, ethnic, and ideological. Prominent among them: agribusiness companies in California and the Southwest; employers of mostly low-wage labor such as hotels and restaurants; a few unions with large percentages of immigrant members; some high-tech companies; some ethnic and religious lobby groups; some higher education groups; and ideological libertarians of both the right and the left.
Together they include only a small part of the US economy and workforce, but a large fraction of immigration lobbyists. In a Washington dominated by interest-group politics and their lobbyists, the fact that these otherwise antagonistic lobbies are in coalition to increase immigration may give some senators the (incorrect) impression that there is a broad base of support.
There is a second puzzle, too: Some political strategists for both the Democratic and Republican parties believe they can gain politically by expanding legal immigration. Each party supposedly will capture disproportionate support from the minority of voters who favor expanded immigration, from legal immigrants themselves once they naturalize, and from rich sources of campaign finance, while not losing support from the majority of voters who do not endorse such actions.
Meanwhile, an April 2006 AP-Ipsos poll reports that immigration policy has risen toward the top of public concerns, and that "the public is keeping close watch on the immigration debate in Congress and reaction around the country."
In reality, no one knows how these politics will play out. Yet one thing is more than clear: Both parties cannot achieve the partisan gains they are being promised. In the two-party American political system, if one party gains, the other loses.
• Michael S. Teitelbaum, a demographer, was vice chair of the bipartisan US Commission on Immigration Reform, 1990-1997.