Out from the shadow of his mentor the late U.S. House Speaker Thomas P. " Tip " O’Neill, Congressman J. Joseph Moakley has grown to be a Washington leader, beloved by his constituents.

Moakley, a South Boston Democrat, announced Sunday that he would not seek re-election to a 16th term in the U.S. House of Representatives because he has an incurable form of leukemia. He is the ranking Democrat on the House Rules Committee, one of the most powerful committees in Congress. Moakley, 73, is also the dean of the Massachusetts delegation.

It was sad news for people in Neponset Valley who have turned to Moakley over the past 28 years for help with all sorts of needs. It was surprise to many in the area who have known Moakley for years.

The congressman has championed causes on behalf of the proverbial " little guy " his whole career, according to Dedham resident Martin Hanley.

" He’s a voice for the powerless, " said Hanley, the founder and organizer of the annual James Joyce Ramble in Dedham.

The race reaches to the core of two of Moakley’s causes: social justice and health care. Each year, the April race is dedicated to a writer who is detained or imprisoned somewhere in the world. The proceeds from race sponsorships and entry fees are donated to the Dana-Farber Cancer Institute in Boston.

Moakley served as grand marshal for the Ramble in 1995, the same year his wife Evelyn died of cancer.

In 1997, " he was kind enough to write up a resolution that was entered into the Congressional Record, " Hanley said.

As a voter and resident of Moakley’s district, Hanley said the announcement has shaken the status quo.

" Today, and for the next few weeks, people are going to realize we have taken a lot for granted, " Hanley said. " He’s like the Bunker Hill Monument, you look at it and it’s there. You take it for granted. "

A perfect replacement could never be found, either, he added. " The 9th Congressional District and the United State Congress won’t be the same without him. He’s cut from a different cloth than everyone entering politics today. "

The congressman is the kind of man who listens to his constituents and tries to help them any way he can, according to Norwood Council on Aging Director Jean Bargfrede said.

" He’s a person who you could present your problems to and it won’t be forgotten, " Bargfrede said. Seniors in his district have turned to Moakley for help with health care and heating assistance, among other issues.

Creating access to health care and having prescription drug coverage for seniors included in Medicare are two of the issues Moakley has on his political agenda.

But always on his agenda is helping his constituents, and that is where Bargfrede and Norwood seniors are very grateful, Bargfrede said. Moakley and his staff were instrumental in obtaining a $600,000 federal grant to build a senior center addition to the Norwood Junior High North.

The total project cost was about $850,000, and the federal grant was administered by the state. When the center had an open house after it was completed, Moakley was present much to the delight of Norwood seniors.

" When he came to the open house, people were just very pleased to meet him and very happy that he took time out of his busy schedule to come down, " she said.

Attending such events is how Moakley does his job. He is known for travelling his district, which stretches from the narrowest streets of South Boston to Neponset Valley to Taunton.

Moakley was elected to Congress from his City Council seat in 1972 when he ran as an independent candidate from South Boston against Louise Day Hicks, whom he lost to in 1970. Since then he has drawn a host of challengers.

This past election, Moakley was re-elected with his widest margin of victory as a congressman. He beat Republican Janet Jeghelian of Westwood and David Rosa an Independent candidate from Taunton.

All through the campaign, Jeghelian said she admired Moakley and believed he was a dedicated congressman. She repeated her comments yesterday.

" I respect the man, " she said.

But having known Moakley for more than 25 years, Jeghelian said she knew it was too early to count him out of the game.

" From the outset, he was the guy to deal with obstacles, " she said. " I don’t rule him out. He’s come from tougher odds. "

Set to announce his retirement in 1995 as his wife, Evelyn, was dying of cancer and he was recovering from a liver transplant, Moakley has said that Evelyn changed his mind. She told him to stay in it, and he did.

Moakley has said he got his start as a hard worker while growing up in a South Boston housing project. At age 15 he joined the U.S. Navy by lying about his age. He returned from military service and went to college and law school.

The lifelong Democrat was elected to the state House of Representatives in 1952, and then to the state Senate in 1965. He gave up his seat in 1970 to run for the U.S. House but lost to Democrat Louise Day Hicks.

The next year he ran for Boston City Council and won. He followed that victory by beating Hicks in 1972 for the congressional seat.

He served in the U.S. House under the late " Tip " O’Neill, who taught Moakley much of what he knows about being a politician and being a political leader, the congressman has said.