The Los Angeles Police Department's plan to map where Muslims live poses a real dilemma for Mayor Antonio Villaraigosa, who is both a great backer of Chief William Bratton and a former president of the local chapter of the American Civil Liberties Union.

What's he going to do? Turn his back on the popular chief, who has become the mayor's partner in running the city? Or will he break the hearts of his liberal Westside supporters, who are already disappointed by the messy end to his marriage?

Such is the life of a mayor who must stitch together a governing coalition in a city confronted with some of the nation's most difficult ethnic conflicts.

The LAPD, by its very nature, is thrust right in the middle. Racial discord is played out on the streets that our cops protect. The department has tried get over the occupying army image of past years, but is given to relapsing, such as when the police pushed around demonstrators and journalists at McArthur Park.

The mapping proposal, as outlined by Deputy Chief Michael P. Downing to a congressional committee last month, is pretty vague.

He said the department is hopes to work with USC' Center for Risk Analysis of Terrorism Events on an "extensive 'community mapping' project. We are also soliciting the input of local Muslin groups, so the process can be transparent and inclusive." He said, "While this project will lay out the geographic locations of the many different Muslim population groups around Los Angeles, we also intend to take a deeper look at their history, demographics, language, culture, ethnic breakdown, socio economic status and social interactions."

Just how will this will be done, and for what purpose? That is a mystery and a scary one. How will the census takers check on social interactions? What will they do when they encounter three or four young men speaking Farsi while having coffee on a Westwood sidewalk? Will the cops believe the men when they say they are Jewish? Will they have to produce proof of synagogue membership? And finally what will the police do with the information after it is given to the 300 officers who work under Chief Downing in the Counter-Terrorism and Criminal Intelligence Bureau.

The mayor said, "Chief Downing has good intentions here." He said that he had only learned of the new program through newspaper articles and at a short briefing.

But the ACLU doesn't like it. Ramona Ripston, the local ACLU executive director, said it reminded her of the old red-hunting days.

Anyone who knows anything about LA history understands what she's talking about.

The counter terrorism bureau has some alarming precedents. One was the infamous "Red Squad" of the 1920s and 1930s, which broke up meetings the cops considered left wing, and hassled, beat and arrested anyone too left of center. The Public Disorder and Intelligence Division followed the Red Squad. It was disbanded when its officers were found to be spying on political leaders and many others thought to be too liberal.

As a former president and board member of the ACLU, the mayor should know the dangers of such out-of-control intelligence units.

I think Chief Bratton is trying to run a good department. He deserved appointment to a second term. But heavy-handed repression is deep in the LAPD soul, as the chief learned at McArthur Park.

The chief needs the mayor. Together, they can get the 1,000 more cops L.A. needs.

And the mayor needs the chief. When they appear side by side on television, as they did on KNBC's News Conference recently, his damaged image is improved. . But Villaraigosa can't be allowed to forget his ACLU past. He can't allow civil liberties to be trampled by the vague police-mapping scheme.