(AP Photo/Charles Dharapak, file)
In a statement, the former six-term congressman said he cares about those seeking decent housing, fair wages and health care. But he added, "The best way for me to contribute to those causes is by continuing my work at Citizens Energy Corp."
The not-for-profit organization provides free heating oil to the poor, but Kennedy likely would have faced questions about fuel it received from Venezuelan President Hugo Chavez.
The decision surrenders a seat the Kennedy family has held for all but two years since 1953, when John F. Kennedy moved from the U.S. House to the Senate, before being elected president in 1960. It became vacant Aug. 25, when Edward Kennedy died at age 77. He was first elected to the Senate in 1962.
It also removes an excuse for three veteran Massachusetts congressmen -- Reps. Michael Capuano, Edward J. Markey and John Tierney -- who have said they are considering campaigns but would not run against a member of the Kennedy family. The senator's widow, Vicki, had previously ruled out a campaign.
In a fiery speech Monday morning to a Boston labor breakfast, Capuano sought to distinguish himself from unnamed competitors.
"Everybody loves you today," the congressman told a crowd of about 400, including Tierney and Markey. "Everybody's for prevailing wage, everybody's for (project-labor agreements), everybody's for this, that and the other thing. Me too. That's good. But when it comes time to make the tough decisions, that's when you start to figure who's with you and who's not."
Markey said before addressing the crowd that he was still weighing a race, highlighting his stature as a 33-year member of the House, honorary title as dean of the New England delegation and chairmanship of the House Select Committee for Energy Independence.
After Kennedy announced his decision, Markey issued a statement saying: "I now must weigh where I can make the greatest impact on the issues facing the people of Massachusetts."
Former Rep. Martin Meehan, who is now chancellor of the University of Massachusetts-Lowell but still has nearly $5 million in his campaign account, had also said he would defer to Kennedy, but he has been lukewarm about a campaign even if Kennedy declined to run.
Another Democrat, Rep. Stephen Lynch, said at the breakfast it's "likely" he will be announcing his candidacy during the next week. The former ironworker, who lives in blue-collar South Boston, said he wanted to wait until after Labor Day.
"I probably won't fit in in the U.S. Senate, but, I think that, in a lot of cases, the people of Massachusetts don't want a senator to fit in. They want them to stand out, and I offer through my experience," Lynch said.
Lynch recalled twice being laid off from shipbuilding and automaking jobs, adding, "I share the experience that a lot of others are feeling right now."
Attorney General Martha Coakley became the first high-profile Democrat to declare for the seat when she announced her candidacy last week. Her supporters lined city intersections for two blocks around the hotel hosting the Greater Boston Labor Council breakfast, testifying to her early organizational advantage in the 90-day sprint to the primary election.
"We're off and running," Coakley said as she shook hands outside.
One prominent Republican, former Lt. Gov. Kerry Healey, announced Sunday she would not run. But state Sen. Scott Brown said he is formally "testing the waters" under federal election law. That provision allows him to raise and spend up to $5,000 assessing a campaign. He expects to announce a decision Thursday or Friday.
The 16-year municipal and state official has also been in the military for 29 years, most recently in the Massachusetts National Guard as a lieutenant colonel in the Judge Advocate General's Corps. His eldest daughter, Ayla, gained national prominence in 2006 as a Hollywood finalist on TV's "American Idol."
"There's a guy in the White House who's cut a somewhat similar path: He was a state senator, a U.S. senator and now he's president," Brown said in an interview.