IT'S BEEN NEARLY three years since, he moved into the neighborhood, but the man with four-years lease on a home in the 1600 block of Pennsylvania Avenue NW now claims he is "proud to be a Washingtonian." To his fellow townspeople, Jimmy Carter's sudden identification with the city he cast as his campaign enemy comes a little late -- though not at all coincidentally; it arrived in time for his appearance before a D.C. Democrats dinner. It was the first time the president has made a major speech aimed at local Washington, which gave him his highest plurality in 1976 -- 82 percent.

"There are really two Washingtons," Mr. Carter now says, the "federal city" and "home-town Washington, where 70,000 people live and work and make a good city function. . . I never confused the two cities, and I have only good things to say about home-town Washington." To hear him tell it, some of his toughest struggles have been the fights for Old D.C.: "The fight to win congressional approval of this amendment [for congressional representation] was not easy," he recalls, adding, "That success was one of the most satisfying victories of my administration."

Many of those who worked the halls of Congress for this amendment have difficulty remembering his exertions. But they shouldn't have too much difficulty taking Mr. Carter up on his offer to work for ratifications by the state legislatures. The amendment needs all the White House help it can get in spreading the word that the District of Columbia deserves representation in Congress. Whatever Mr. Carter can do on this score would be downright neighborly.