D.C. Council member Adrian M. Fenty announced yesterday that he is running for mayor of the nation's capital, becoming the first official candidate in a large field of potential contenders to replace Mayor Anthony A. Williams.

Standing on a shaded sidewalk in front of the Mount Pleasant rowhouse where he was raised, Fenty (D-Ward 4) cast himself as an engaged and energetic politician dedicated to a "vision of a better, more inclusive city," in which the poor are not forgotten and children attend decent public schools.

"You have told me you want a mayor to unite us and inspire us," Fenty told an enthusiastic crowd of about 100 people. "And with your support, that is what I intend to be."

If elected, Fenty, 34, would be the youngest District mayor in three decades of self-government. In a little more than four years on the D.C. Council, Fenty has emerged as both a highly responsive ward politician and a charismatic figure, as comfortable in the poor, black neighborhoods east of the Anacostia River as in the white, wealthy ones west of Rock Creek Park.

To voters citywide, he said, "I will talk with you, and I will work with you as I have the citizens of Ward 4."

That line was seen as a dig at Williams (D), who has yet to say whether he will seek a third term. During his six years as mayor, Williams has been criticized as aloof, an outsider who never connected with ordinary people. Fenty has been one of his harshest critics, accusing the mayor of neglecting schoolchildren and the poor while catering to downtown business interests and agreeing to build a new ballpark for "millionaires."

Last week, the mayor struck back, describing Fenty as "more talk [and] less action than anybody I've ever seen." Yesterday, Williams declined to say much about Fenty's candidacy, noting that the election is more than a year away.

"I really don't want to turn this into an election fight at this time," Williams said.

Later, he jabbed at Fenty, saying the council member failed to contact him about the proposed closure of Walter Reed Army Medical Center, a major military installation in Fenty's district.

"Maybe he's too busy to call me," Williams said.

With Williams's political future uncertain, a cast of potential candidates is lining up to replace him, setting the stage for what could be the longest and most expensive mayoral race in D.C. history. Over the past six months, Fenty and three possible contenders have raised a total of more than $800,000 through exploratory committees. The others -- council member Vincent B. Orange Sr. (D-Ward 5), former D.C. Democratic Party chairman A. Scott Bolden and lobbyist Michael Brown -- say they will make a decision about the race by summer's end.

In addition, council member Jack Evans (D-Ward 2) has commissioned a citywide poll and is considering forming an exploratory committee, aides said. Evans was preparing to undergo eye surgery today and was not available for comment. Council Chairman Linda W. Cropp (D) also is mulling the race, as are council member David A. Catania (I-At Large), former U.S. attorney Eric H. Holder Jr. and former Verizon executive Marie C. Johns.

Fenty brought the exploratory phase of his campaign to a close yesterday and is planning campaign kickoffs in each of the city's eight wards. He has spent his $300,000 exploratory account, he said, and expects to raise an additional $1.5 million for the coming campaign.

Though no independent polls have been conducted, Fenty is viewed by the mayor and others as a serious contender. He is popular in vote-rich Ward 4, where he defeated veteran council member Charlene Drew Jarvis (D) on a shoestring budget in 2000 and was unchallenged for reelection last year.

More recently, he has attracted a wider following of liberal and good-government activists who like his stated commitment to D.C. statehood, smoke-free buildings, affordable housing, community economic development and better public schools.

Yesterday, Fenty said Williams deserves credit for reviving a city that once hovered near bankruptcy. But now, he said, it's time to usher in "a new era where we no longer judge ourselves on the dark times of the past, but against what we want our future to look like."

Council member Adrian M. Fenty basks in supporters' applause during the announcement. Right behind him are father Phillip, mother Jan and brother Jesse.

A supporter waves goodbye to Fenty and his wife, Michelle, after the announcement. Fenty said he will try to unite and inspire the city.