While the Carter administration gropes for an urban policy to channel jobs and new life into the nation's cities, Massachusetts has one in place - and it's working.

Michigan, looking for ways to reinvigorate Detroit and its other imperiled industrial cities, has begun to implement an urban strategy almost as effective as the Bay State's.

And California, now a global symbol of sprawl development that robs center cities and older town centers of their lifeblood, may have a sweeping urban strategy in place by the start of 1978 - if Gov. Edmund G. Brown Jr. has the political courage to implement the blueprint for city and town survival developed by his own Department of Planning and Research.

Mindful of the gross negligence with which state governments have traditionally treated cities, many mayors and minority spokesmen assume the only hope for urban America lies with huge infusions of federal aid But wise heads have long said the states could become the cities most valuable allies if they would only shift their immense powers - over taxes, roads, land use, govenment job location and federal aid programs they administer - from the detriment to the help of urban areas.

In Massachusetts and Michigan, that's precisely what's happening - thanks to two strong governors, Michael S. Dukakis and William G Milliken.

Long before he became governor, Dukakis says, he decided there was something "radically wrong" with policies in Massachusetts - repeated nation wide - that fostered "scatterization" of development and jobs the most were left in declining urban neighborhoods."

His solution didn't lie in huge appropriations for cities or vast land-use planning efforts, but rather in turning all the state's existing regulatory power and public investment programs, in a single-minded fashion, to one goal: reinforcement of existing city and town centers.

Frank Keefe, a 28-year-old "action oriented" planner who'd already done much to revive the old mill city of Lowell, become Dukakis's state planning director and chairman of a seven-member economic-development cabinet charged with making the urban-reinvestment strategy a reality.

The development cabinet hunkered down with leaders in each of the state's old urban centers. Each city was urged to identify what made it distinctive interesting old buildings or squares, ethnic enclaves, special natural settings. Even such supposed liabilities as deserted mills or decaying waterfronts, it was suggested, could be recycled for housing, industry, shops, restaurants and recreation as part of an overall strategy for downtown and neighborhood revitalization.

Cities were offered "one-stop shopping" for needed state assistance, from clearing state building-code obstacles to commitment of funds - virtually unprecedented in the nation - for state parks in downtown areas.

The word went out to industries and developers, says Keefe: "We'll bust our backsides to help you develop in a city industrial park, to rehabilitate an old mill building, to engage in a downtown recycling project. But it's counterproductive for us to spend money extending a sewer line or highway to your development out in the middle of nowhere."

It's just as important, Dukakis says, to reinforce town centers as those in larger cities. The state fought successfully to keep post offices in the centers of Amherst and Andover "instead of putting them out in the boondocks,"

Massachusetts now boasts a moderate flow of industries selecting in-city locations over the suburban sites so favored in recent years. The prospects for industries in cities are the brightest since World War II, Dukak is claims.

Shopping-center and suburban-sub-division builders oppose the Dukakis policy, but he believes most suburbanites want a respite from intense development pressure. He says that growth policy statements drawn up by 330 Bay State communities show that "villages don't want to be suburbs, suburbs don't want to be cities, and cities don't want to be wastelands."

When the nation's governors met in sweaty, striving Detroit last month, Milliken was able to show them both the splashy new Renaissance Center and several encouraging new inner-city housing and factory projects made possible by special state assistance. State governments, Milliken told his colleagues, "have a vital , necessary role to play in the saving of our cities."

Under Milliken, Michigan has sharply increased state revenue-sharing for cities; made a state "equity" payment - atmost $30 million this year - for services. Detroit provides its suburbs and the state; enacted a 12-year tax benefit for factory improvement a new construction; and approved a job-development authority.

Though state police are traditionally out-country, nonurban law enforcers Milliken threw them into Detroit to help an undermanned city police force stop a wave of felonies on city express ways. Now, despite legislative opposition, he wants to expand the program to other large cities, including Grand Rapids and Flint.

Milliken acknowledges his pro-city policy is less than popular with some fellow Republicans from suburbs and rural areas. But unattended, he told me, city problems will inevitably infect suburbs; abandoned cities would not only mean forsaking the billions already invested there, "but would mean we're abandoning the whole country."

California's proposed plan borrows, heavily from the Massachusetts model, decrying spread development. The 4 to 8 million additional population California expects by 2000, the plan says, can easily be accommodated in undeveloped land in existing cities and suburbs (54,000 acres in Los Angeles County, alone), or on the immediate edge of built-up urban areas.

California is currently gobbling up open spaces and farm lands at an alarming rate, notes chief state planner Bill Press. The process, he says, is incredibly wasteful of land, energy, tax dollars and underutilized buildings, streets and schools in already settled areas and the human energy of Californians obliged to commute to work over long distances.

If Brown adopts the plan, all state agencies would be obliged to tailor their policies toward urban conservation - a radical break with past practice. Brown would encounter opposition from localities forced to yield land use decisions to regional authorities from affluent communities obliged to shares taxes with poorer communities on a regional basis, and real estate and construction interests whose exploitative development tactics would be curbed.

Yet if the most populous state does opt for urban conservation, the idea of states as city savers could gain such momentum that it would become the rule, rather than the rare exception, in years to come.