PRESIDENT Clinton has returned to town to finish a task begun by George Bush.
One of the most pressing matters on Mr. Clinton's fall agenda - pressing because of a Jan. 1 deadline to implement the pact - is passing the North American Free Trade Agreement (NAFTA).
NAFTA was envisioned and negotiated by then-President Bush, and the Republican roots of the agreement are showing. As Clinton returned to town, he was greeted by a warning on a Sunday talk show from Rep. David Bonior (D) of Michigan, the House majority whip, that two-thirds to three-quarters of House Democrats will oppose NAFTA. Most Republicans in both chambers favor it.
Democratic support for NAFTA is weakened by concern that American jobs and environmental standards will be undercut by Mexican competition.
But the politics of NAFTA also tap another issue with rising power, one that some political analysts and strategists foresee as a dominant concern in the 1990s - immigration.
In a United States where middle-income jobs feel increasingly insecure, the urban underclass seems increasingly volatile and alienated, and traditional Anglo-American, middle-class culture is increasingly on the defensive, politicians are increasingly seeking ways to control American borders.
One selling point for a free-trade agreement with Mexico has been that it would make Mexico more prosperous and gradually cut the incentive for Mexicans to seek work in the US, where wages are nine times higher on average.
Mexicans form the largest group of immigrants to the US, and gauging by the legalization programs of the 1980s, they account for about 75 percent of illegal immigrants.
But the effect of NAFTA on immigration is neither clear nor simple to foresee. Most economists who have set up forecasting models indeed see substantial long-term benefits to the Mexican economy that would eventually stem the flow of Mexican workers into the US. But it is likely to take five-to-15 years for that effect to become significant.
In the meantime, NAFTA may actually increase emigration from Mexico.
American grain and corn farmers produce for roughly half the cost per ton of small-scale, inefficient Mexican farmers. Those Mexicans are widely expected to be among the first economic casualties of NAFTA. Once displaced, many may head north and begin the traditional climb into the American economy as farm workers.
Another possible source of increase is that Mexican production geared for US markets is likely to develop along the country's northern border, bringing workers into the orbit of the lucrative US job market. Illegal immigrants have often moved first into growing Mexican border cities such as Tijuana, then continued north either permanently or on a seasonal basis.
One study, commissioned by the National Commission for Employment Policy, an independent federal agency, estimates that NAFTA would add "at most" 100,000 Mexicans a year to US immigration flows through the 1990s.
Of those, about 10,000 would stay to become permanent residents each year, based on past trends. NAFTA, therefore, could add 800,000 to 1 million illegal Mexican immigrants over a 5-to-15-year period, according to the study.
At some point, economic growth in Mexico and relative complete adjustment to an open economy would be expected to neutralize the incentives for Mexicans to emigrate.
In the first decade of the next century, Mexican immigration would decline, according to the study.
Some other studies are more optimistic about NAFTA's effect on cross-border migration. A study for the US International Trade Commission estimates that if NAFTA causes no economic growth in Mexico, American competition will drive a cumulative total of 610,000 Mexicans north into the US over the course of many years.
But if American investment in Mexico is substantial and agricultural trade barriers erected by Mexico are phased out slowly, then immigration would decline slightly under NAFTA from the beginning. The ITC study estimates a decline in Mexican emigration to the US of about 2,000 people a year under this scenario.
All these forecasts are set against current trends of high illegal immigration from Mexico, a country that is already working to open its markets and reform landownership policies.
Some NAFTA advocates warn that if the agreement is scuttled, Mexico will not simply hew to the same course. Instead, the free-trade forces that hold sway in Mexico now might lose credibility and confidence in American support.
NAFTA is already under way in practice in Mexico, says Hoover Institution senior research fellow William Ratliff. But it is running on anticipation and general understandings.
If the agreement is not set down in law soon, he says, the trend toward openness could reverse in Mexico. "The amount of illegal immigration, if things fall apart in Mexico, is going to go up astronomically. And other governments in the hemisphere are watching what we do in Mexico."