TO HIS CREDIT, President Carter is trying again to persuade Congress to extend some special help to cities and counties that are economically hard pressed. Moreover, the plan sent to Congress Tuesday is a carefully tailored one that responds well both to urban problems and to the criticisms that torpedoed a much larger proposal last year.

Objections to this kind of aid have focused on two points: timing and targeting. The program began in 1976 as counter-cyclical or anti-recession. That aid was meant to stop when the national unemployment rate dropped below 6 percent. However, the general recovery did not end the distress of cities with chronically high joblessness, heavy taxes and lagging growth. Areas such as Newark, Detroit, New York City and Oakland not only wanted more special aid; they needed it. But various factions in Congress were unable to agree on how local fiscal stagnation should be measured and how many areas should get how much help.

Mr. Carter's new proposal has two parts. The first phase would distribute $250 million in this fiscal year and $150 million in fiscal 1980 to urban and rural areas with unemployment rates of 6.5 percent or more. Only 1,231 localities would qualify, with about one-third of the funds going to the 10 major cities often regarded as most distressed. The greatest aid per capita would go to Newark, where taxes are truly oppressive and the unemployment rate is around 13 percent. The District and Baltimore would each receive over $3.9 million. That may sound odd, since Baltimore is larger and often thought of as fiscally more strained. It does show that the formula isn't perfect -- but it is also a good reminder that the District has more chronic unemployment than many people realize.

In general, this is much better aimed than last year's administration plan, which would have spread the "special" aid among some 26,000 communities. Accordingly, it may be too narrowly targeted to suit Congress, which prefers to give something to everyone. Thus there is political as well as economic foresight in the second part of Mr. Carter's plan, which would provide a form of counter-cyclical aid to many more communities and the states if the economy does deteriorate and the national unemployment rate rises to 6.5 percent or more. The administration describes this as an "insurance policy" or "safety net" and no doubt devoutly hopes that it will not have to be used. Whatever one's view of the economic future, though, the standby program nicely complements the aid for localities that are hurting most now. The combination deserves broad support.