WITH 15 MONTHS to go in his second term, it's too soon predict the legacy of D.C. Mayor Anthony A. Williams, who announced yesterday that he will not seek reelection. It is also too soon to render a final judgment on his service as chief executive. It is not, however, too early to take the measure of Mr. Williams against the three other occupants of the job he has held since Jan. 4, 1999. If success can be gauged through comparisons, Mr. Williams will go down as the most accomplished mayor in the city's 30 years of home rule.

When Mr. Williams took the oath of office, the District was being run by a congressionally created, presidentially appointed financial control board. The city was in financial ruin. Wall Street had withdrawn its welcome mat, and the local government was discredited both in the eyes of its residents and on Capitol Hill. Several city agencies were being operated by court-appointed receivers, and middle-class residents, fed up with crime and inferior basic municipal services, were abandoning the District in droves.

During Mr. Williams's tenure, the control board departed two years before deadline, court receiverships were lifted, the city's budgets were annually balanced, Wall Street upgraded D.C. bonds from junk status to an A rating, violent crime declined, homeownership rates rose and the D.C. treasury was filled with a healthy surplus, including a $300 million rainy-day fund. Doors are open to the mayor at both ends of Pennsylvania Avenue NW. A city once shunned is now the place to be, during evening hours as well as during the day.

To say that Mr. Williams achieved this alone would be preposterous, but to suggest that this turnaround could have occurred without him would be equally absurd. From the financial control board to Wall Street, Congress and the White House, Mr. Williams emerged as the essential Washingtonian in the District's rebirth and return to a solid foundation.

It should also be noted that the mayor -- unless there is a miraculous conversion in the next 15 months -- will not be recorded as one of the city's better politicians. In fact, Mr. Williams started as a political amateur six years ago and never broke into professional ranks. From his first decision to relocate the University of the District of Columbia from Northwest Washington to the Saint Elizabeths Hospital campus, to his flip-flopping over school governance, to his current about-face on a courageous decision to oppose building a new hospital on the site of the old D.C. General Hospital, the mayor has demonstrated a consistent inability to hold his ground, mobilize support and see a difficult position through to the end. As Mr. Williams observed in a meeting with Post editors and reporters this year, the post of mayor requires energy, tenacity, discipline and focus, and, we might add, intelligence and financial ability -- the last two of which he has in abundance. Organizing political campaigns and identifying political talent never emerged as the mayor's strong suits, and he has the record to prove it.

None of that takes away from his overall positive performance when matched against the records of his predecessors. Walter E. Washington, the city's first elected mayor, skillfully managed the city's transition from an appointed to an elected government and established important linkages in the city, Congress and region that served the District well. But no other D.C. mayor confronted as many problems and addressed them as successfully as Tony Williams.