BOSTON — Senator Kerry’s decision not to seek the presidency in 2008 is sparking a gold rush among Democratic presidential hopefuls eager for a piece of an organization that won the 2004 nomination.

Although Mr. Kerry’s popularity has ebbed recently — a fact that helped prompt yesterday’s decision — political operatives view his campaign machine as formidable. Mr. Kerry’s political committee, Keeping America’s Promise, distributed $4 million during the 2006 election cycle. His field operatives won an unforeseen victory in Iowa in 2004, when most political observers were taken with the flavor of the month, Governor Dean. And Mr. Kerry’s personal and political contacts were key to victory in the crucial early contest of New Hampshire.

“I think it frees up a lot of people who are waiting for the senator to make a decision. A lot of activists I knew were staying loyal until he made his decision,” the chairman of Mr. Kerry’s campaign in New Hampshire in 2004, Bill Shaheen, said of the senator’s decision.

Mr. Shaheen, who is the husband of Jeanne Shaheen, the former governor of New Hampshire, said he has been personally contacted by Governor Vilsack of Iowa, Senator Dodd of Connecticut, Governor Richardson of New Mexico, and Senator Clinton of New York. He added that representatives of Senator Obama of Illinois and John Edwards have also reached out to him.

The support of well-known New Hampshire activists, such as Mr. Shaheen, as well as local Granite State political bosses, can make a difference for presidential hopefuls, particularly in the dense urban neighborhoods of Manchester. “It is a prize,” Mr. Shaheen said of Mr. Kerry’s organization. “It’s building an organization so you can identify every voter who’s going to vote. And personal relationships. They vote for people because they trust you. A lot of political operatives in Manchester can deliver 200 votes.”

In 2004, Mr. Kerry raised more than $250 million during the 2004 election thanks in part to the vice chairman of his fund-raising committee, Alan Solomont. “He had the largest leadership PAC of any candidate this cycle,” Mr. Solomont, who served as the finance chairman of the Democratic National Committee’s finance committee during the Clinton administration, said. “I’m sure people who are with John Kerry will look at the field and go in a number of different directions.”

A former chairman of the DNC, Steve Grossman, supported Howard Dean in the 2004 Democratic primary and then backed Mr. Kerry in the general election. While Mr. Grossman declined to discuss which candidate he will support in 2008, sources said he will bring his fund-raising prowess to Mrs. Clinton. There was great optimism regarding Mr. Kerry’s chances during much of 2006. Massachusetts’s junior senator traveled across the country on behalf of candidates and built relationships with his campaign committee. That good feeling ended after Mr. Kerry’s botched joke at the end of October from which he never recovered. Following a series of strong speeches in the early fall, Mr. Kerry receded from public view after the “joke” flap in which he appeared to insult the intelligence of American troops. Into that vacuum other candidates, such as Mr. Edwards and, notably, Mr. Obama, rushed to provide an alternative to Mrs. Clinton. Today, the mood in some quarters of Boston was one of profound regret.

“I’m disappointed. I worked hard to get John elected president. I believe he would have made a great president,” Mr. Kerry’s brother, Cameron Kerry, told the Sun. “You’ve got to deal with the realities. And looking at things … the way he can be most effective on the issues he cares about is in the Senate. There’s a lot that he can do there.” Many among the local political class were unwilling to speak openly about the future of the presidential race. While there was speculation about operatives and fundraisers signing on with Mr. Obama, few, out of deference to Mr. Kerry, wanted to talk about that today.

Eyes in Boston were on members of the Dewey Square Group, such as founder Michael Whouley, who served as Mr. Kerry’s chief strategist in the 2004 campaign. Mr. Whouley is the street-smart politico who cautioned Vice President Gore against conceding the night of the 2000 election. He did not respond to a request for an interview. His colleague, Charles Campion, said his own focus was on running the company. “A lot of the campaigns have been cautiously talking to people,” Mr. Campion said, adding that, right now, he was “just holding off a little bit.”

Dan Payne, a Democratic analyst whose relationship with Mr. Kerry began in 1972, said the ultimate prize for the other presidential contenders would not be operatives but the support of Mr. Kerry himself. “He has built up an apparatus and has loyal friends,” said Mr. Payne, who helped get Mr. Kerry elected to the Senate in 1984 but did not work for him in 2004. “He does have a big data base of 3 million names. It is a big resource. But those people are not going to do anything in lockstep.” At least two Democratic presidential contenders put out statements yesterday praising Mr. Kerry. Mr. Obama said, “From his earliest days in Vietnam to the presidential election in 2004, John Kerry has fought for his country and his ideals. I am proud to call him a friend and a colleague in the United States Senate and know that he will continue to serve his country with honor and distinction in the years to come.”

And Governor Vilsack of Iowa released a statement saying that he was on Mr. Kerry’s short list for the 2004 vice presidential nomination. “I look forward to continuing to work with Senator Kerry to change our nation’s course in Iraq and fight for the priorities of working Americans,” Mr. Vilsack said.

An e-mail from Mr. Kerry to supporters yesterday said, “I’ve concluded this isn’t the time for me to mount a presidential campaign. It is the time to put my energy to work as part of the new Democratic majority in the Senate, to do all I can to end this war.”

The e-mail said, “Above all else, the mission we must all join is to end the war in Iraq. Our first step toward that goal is to force President Bush to set a deadline to redeploy our troops.”