THE nation’s mayors, meeting in Chicago, have sent their plea for aid to the President-elect. Unfortunately, although they indicated what they would like the nation to do to help the cities, they appear to have remained silent concerning what the cities are prepared to do to help themselves.  A review of our foreign-aid experience may help to clarify some of the problems of mounting a program of domestic municipal aid on a comparable scale. For example, a Marshall Plan for cities has frequently been advocated, notably by the late Whitney Young.  However, the idea has been little more than a catchy slogan to symbolize big federal dollars and contrast our willingness to aid in the recovery of Europe with our grudging support of our own cities. Consideration of the Marshall Plan and the reasons for its success and the failures of our programs elsewhere than in Europe has much to offer those seriously concerned with structuring a federal aid program with any real promise of achieving for our cities what the Marshall Plan did for the nations of Europe.