PRESIDENT REAGAN got a firsthand look this week at what public and private partners can do to revitalize an aging city. The president was in Baltimore selling his "new federalism" version of that partnership, in which the federal government would play little if any role. Perhaps his tour will cause him to modify his view.

Baltimore's Mayor William Donald Schaefer has been one of the most successful of the "wily stalkers of federal aid" to whom the unsanitized version of the administration's national urban policy report referred. But he has used that aid imaginatively to engage the business community in rebuilding Baltimore on a scale that federal funds alone could not have supported. The Inner Harbor project drew funds from numerous federal and local sources. The job center the president visited combined business and Commerce Department money, and its youthful employees were recruited and prepared for work by CETA programs.

There is much in the Baltimore experience--and in cities around the country--that supports the president's idea that revitalization works best when local business and community interests are involved. And Baltimore has also shown that the flow of good ideas doesn't always start at the federal level--the city's innovative job programs, for example, were widely emulated by other localities. But in all these projects federal leadership and resources were an indispensable catalyst for local action.

Federal money can certainly be used to greater advantage when, as in Baltimore, it helps generate local private and public investment. Federal regulations can also be needlessly burdensome--although cases of waste and misuse of federal money have usually come from too little federal direction rather than too much. But there is no reason to expect private business, with or without local encouragement, to be the lone savior of the cities.

Many companies have discovered social consciences in recent years. But for every shining example of corporate beneficence there is a counter example in which business exploited the resources of a community and then, as in the mining communities of the West, moved on, leaving behind only a gaping hole. Federal leadership has been an indispensable ingredient in the economic development of the country, from the opening of the West and the revolution in American agriculture to the building of a modern transportation system. There is still an important role to be played in ensuring that when local government and private interests coalesce, the larger public interest is also served.