"It's got nothing to do with politics," the Quincy Democrat said today. "Life is about change. I think it's healthy. It's time."
The 68-year-old lawmaker said he has been considering leaving the House for several years, but was talked out of it two years ago by the late Senator Edward M. Kennedy, who convinced his friend he should stay and help President Obama with his first-term agenda.
"He said, 'Come on -- this is a new time. It's a new era. We [will] have a new president. We're all needed," Delahunt recalled Kennedy telling him. Once Kennedy died last year, Delahunt said he grappled with whether to stay and work on the issues Kennedy held dear.
"Clearly, since his death, there's something missing. There's a void. With the void, you feel the need to be here because there's much to do," Delahunt said wistfully in an exclusive interview.
But the congressman said he concluded that after nearly four decades in public service, the grueling House schedule was taking its toll on his personal life.
"I've got a granddaughter," the divorced father of two said. "Given the pace down here, I don't want to miss out on her childhood, her first year."
The congressman has faced recent questions about the handling of the 1986 Amy Bishop shooting case, which occurred when he was Norfolk County district attorney. Delahunt has said consistently that his office was not told that Bishop fled with a loaded weapon after killing her brother in what police then called an accident.
But the case has absolutely nothing to do with his decision to retire, Delahunt said. Several of the congressman's friends and associates confirmed that the lawmaker has been mulling his departure for years, and very seriously considering it for many months.
Voters in Delahunt's 10th District gave Republican Scott Brown his best margins in the state in the special Jan. 19 election to fill Kennedy's seat. But Delahunt said the wave of anti-incumbent anger also did not affect his decision.
Delahunt's retirement is the 17th among House Democrats, and the third among lawmakers with close ties to Kennedy. Senator Christopher Dodd, Democrat of Connecticut and a close Kennedy friend, announced his retirement in January; Rhode Island Representative Patrick Kennedy, the late senator's son, followed suit last month.
Delahunt told Obama about his decision this afternoon at a bill-signing ceremony for a travel and tourism promotion measure Delahunt wrote with Representative Roy Blunt, Republican of Missouri. The president said he understood and wished him well, said Delahunt, who was the first member of the Massachusetts delegation to endorse Obama in the primaries.
Many Democrats -- including House Speaker Nancy Pelosi and House Majority Leader Steny Hoyer -- urged Delahunt to stay another term, worried that the volatile campaign environment could give the GOP a chance at the seat. Joseph P. Kennedy III's decision earlier this week not to seek the seat makes Democrats even more nervous.
But the congressman -- while declining to name a favored successor -- said he is "confident it will stay Democratic."
The lawmaker established himself in Washington as a leading voice in his party on Latin American and Caribbean issues, traveling many times to Cuba, Haiti and Venezuela, where Delahunt negotiated with president Hugo Chavez to provide discounted oil from Venezuela, the fourth largest supplier of foreign oil to the United States.
He also hosted a "Grupo de Boston" weekend in the Cape with Venezuelan government and opposition leaders, hoping to get the feuding sides together by having them spend time together in a neutral place.
One of the House's most ardent and reliable liberals, Delahunt has developed many close relationships with Republicans, including Blunt, the former Republican Whip.
Representative Jo Ann Emerson, Republican of Missouri, counts Delahunt as one of her closest allies and friends in the House -- even when the two end up on the opposite side of an issue. "In spite of being very liberal, he's very open. He wants to listen to your side of things," Emerson said.
Working with then-Illinois Republican Representative Ray LaHood, a death penalty proponent, the anti-capital punishment Delahunt spent years going from member to member to win support for a measure giving death-row inmates greater access to DNA testing that could prove their innocence. The bill became law in 2004.
"He votes like a liberal whack job," quipped Representative Steven LaTourette, a conservative Ohio Republican who worked with Delahunt on ethics inquiries and the examination of the FBI in Boston. "But when it comes to working together, he is the person I want to be at the head of that team."
About Political Intelligence
Glen Johnson is Politics Editor at boston.com and lead blogger for "Political Intelligence." He moved to Massachusetts in the fourth grade, and has covered local, state, and national politics for over 25 years. E-mail him at email@example.com. Follow him on Twitter @globeglen.