THIS SUMMER'S uproar over efforts to build a day-laborer center in the western Fairfax County town of Herndon -- a center whose principal users would be undocumented immigrants -- was the occasion for some self-satisfied smirks across the Potomac River in Maryland. At least a few civic figures and elected officials there convinced themselves that Montgomery County was fundamentally more progressive on the question of low-wage workers, illegal immigration and much else, and therefore immune to an unseemly, Herndon-style hue and cry. As Del. Ana Sol Gutierrez (D-Montgomery), put it, "we do not encourage the hatemongering and xenophobia displayed in Virginia."

Alas, scarcely a week or two after Mrs. Gutierrez uttered those words to The Post, Montgomery County was facing its own brawl over a proposed shelter for day laborers, this one in Gaithersburg. City residents, angry that there had been little opportunity for public input, denounced the center even as renovations to prepare for its opening went ahead at a cost to the county of more than $100,000. Unlike Herndon, which took a damn-the-torpedoes approach to criticism, Gaithersburg backed down. The shelter there, which was to serve dozens of workers -- most of them Hispanic immigrants -- who currently await work each morning in a church parking lot, is a dead letter.

Disputes such as those in Herndon and Gaithersburg are both like and unlike classic not-in-my-backyard brawls. The similarity is that residents are genuinely, and justifiably, concerned about the negative aspects of day-laborer centers, including increased traffic, noise, litter, petty crime and impact on property values. The difference is that the disputes over the centers focus in part on the fact that many of the laborers are illegal immigrants -- the byproduct of a failed national policy. Cities and suburban localities are dealing with a rising tide of undocumented aliens they have no power to control. In economically robust places with negligible unemployment, like Fairfax and Montgomery, attitudes toward these immigrants are deeply ambivalent. On the one hand, their services are in enormous demand, and there is no one else to fill their niche in the labor market. On the other, no one wants groups of men loitering on the corner -- and so the illegal status of many is used as an argument against services for day laborers generally.

Montgomery County, where 26.7 percent of the population was recorded as foreign-born in the last census, is not hostile territory for immigrants. A day-laborer center has operated smoothly in Silver Spring for a decade. Another, in Wheaton, opened recently without great ado. The opposition in Gaithersburg might easily have been avoided, as city leaders acknowledge now. They erred on two counts: by failing to provide an adequate opportunity for public comment and by locating the proposed shelter too close to a residential area.

Officials rightly say they will try to find a new site for a day-laborer center somewhere else in or near Gaithersburg. Let's hope they proceed more carefully this time. The critics will still cry foul, arguing that taxpayers should not be forced to subsidize lawbreakers -- that is, immigrants who have entered the country illegally. But they provide no practical alternative to addressing what should be a federal law enforcement matter. The real choice is between the status quo -- day workers loitering around convenience stores, churches and street corners -- and modest shelters. The latter choice is more sensible.