IT WAS A wise move. Mayor Martin O'Malley's decision not to run for governor ensures that Baltimore will continue to have the forward-looking and effective leadership it so desperately needs in its struggle to overcome decades of decline. With Mr. O'Malley staying at City Hall, there is hope for a turnaround.

But "the most difficult political decision of my life" is not enough. Now that he is free from short-term considerations, he should review the progress of his administration. He is halfway through his unusual five-year term. The question in all areas -- from housing to public works to policing -- should be: Is this the best we can do?

If not, changes are in order so that this indeed is "going to be a tremendous decade for Baltimore," as he predicted at a news conference yesterday.

Mr. O'Malley's decision does not remove him from state politics or change his conviction that the Maryland Democratic Party is adrift. And while he pledged to support Lt. Gov. Kathleen Kennedy Townsend, he made it clear he will continue to speak out and "demand more principled leadership" on such critical issues as growth, mass transit and the economic future of the city and the region.

This is a perfectly laudable and constructive approach, if the goal is to ensure that such issues become a central part of the campaign between the two likely nominees, Ms. Townsend and Rep. Robert L. Ehrlich Jr. But unless it is done tactfully and with thought, it could be seen as snide carping.

This is a particularly sensitive issue because Mr. O'Malley's decision is unlikely to end his political rivalry with Ms. Townsend. They don't have to become close friends, but they must recognize that Baltimore can either be an asset or a liability for Maryland and that the city's revival cannot be accomplished without aid and sympathy from Annapolis.

This is the message Mr. O'Malley must deliver to Mr. Ehrlich as well.

Those who promoted Mr. O'Malley's gubernatorial candidacy argued that he had a unique window of opportunity this year that would close and doom his political future. Such speculation is pure balderdash. The 39-year-old mayor's prospects are as bright as ever. He could be a U.S. senator one day, for example. The only thing that changed yesterday was that the governorship no longer is in the cards for him.

The presence of 10 Baltimore and Washington television crews at the announcement attested to Mr. O'Malley's growing political stature and his exceptional star quality. His decision to stay out of the governor's race may indeed increase his attractiveness as a future candidate. After all, wasn't he supposed to be too opportunistic and aggressive not to let this chance pass?

Like previous mayors, Mr. O'Malley has done some easy tinkering. However, he has not touched the tough part -- seeking reforms in the way Baltimore is governed and modernizing the delivery of city services. Such overhauls would be controversial, but are sorely needed. He should now undertake them -- and secure a position for himself as a great mayor.