Thirty-five years ago, at the end of the Viet Nam war, there was a mass evacuation of Vietnamese orphans who had been adopted by Americans and other nationalities. One of the parents anxiously waiting for news of Operation Babylift was one William Delahunt.

It was a nerve-racking time. Mr. Delahunt thought his new adopted daughter was on the first flight out. Then he learned the first flight crashed.

But despair turned to joy. She was safe on the second flight. And so the Delahunts gained a daughter, Kara Mai.

It’s a nice personal story. The thing that makes it a nice political story happened later, when the Delahunts wanted to take her to Germany and had passport problems, because Kara Mai was not considered an American citizen, even though she was their adopted child, and had lived in America from the age of four months.

So Bill Delahunt, congressional representative for the tenth district in Massachusetts, went to work to change that. Now, at the end of his long political career, he claims his success in effecting that change as perhaps the most satisfying achievement of 39 years of elected office.

“It was certainly one of the most poignant moments,” he said this week. “That day in February 2001, when a bill was signed into law, that I authored, that conferred automatic citizenship on children who were legally adopted from overseas.

“Approximately 140,000 children became citizens automatically on one single day, the most ever in the history of the country.”

He announced on Friday that he will not seek reelection.

When politicians quit, claiming a desire to spend more time with family and friends, it is often a cynically-received excuse. But not always, and congressman Delahunt can point to some very specific stimuli in his case.

For one, Kara Mai made him a grandfather for the first time last year.

“Now I have this beautiful grandaughter. I don’t want to miss any time. That’s one reason I’m coming home.”

But not the main one. The main one is the death of Sen. Edward M. Kennedy last year. The two men were close. Indeed, were it not for Senator Kennedy, he may well have quit sooner.

“I had been inclined to do it two years earlier, but Ted said ‘Let’s stay and enjoy having a President we both endorsed.’

“I reminded him I endorsed Obama before he did.

“Then abruptly he passes from this brain cancer. It’s things like that — and it can be a friend or a family member — but it gives us pause to reflect on our own mortality. We all only have limited time.

“I have held elected office for 39 consecutive years and I’m going to be 69 in July. For everything there is a season. This was my season to step aside.”

There is a neat circularity to the Delahunt political career. It was a Kennedy who helped him realize it was time to quit. And it was a Kennedy who got him into politics in the first place.

“I’m one of those who were inspired to public service by Jack [President John F.] Kennedy. In 1960 I was cochairman of Students for Kennedy at Middlebury College in Vermont,” he said.

“It was a very exciting time. In the 1960s there was the civil rights movement, the Viet Nam war, the era of Jack Kennedy, Martin Luther King. I was swept up in the sentiments of those times. That government could do good, could change things.”

There was no chance he would become a dentist, as his mother hoped. He went into law, preparing himself to be the first person in his family ever to be involved in the political game.

“Although,” he laughed, “I did have a grandfather who was one of the leaders of the 1919 police strike, who, as the family tells it, was personally fired by Calvin Coolidge. Maybe that’s why I became a Democrat.”

He was first elected a councillor in his home town of Quincy, sworn in January 1972.

From there it was on to state politics, notably for 22 years as a district attorney in the Boston area, and thence into the federal sphere.

“I’m the first native son of Quincy since John Quincy Adams to hold this Congressional seat,” he said.

And when it was time to announce his plan to retire, he made the announcement from those council chambers, “because it began there and I thought that was apropos; right across the street from there is the Church of the Presidents, where John and John Quincy Adams are buried.”

Looking back, of what is he proud?

Well, we know one thing: writing the language implementing the Hague convention on International Adoption in the 2000 Intercountry Adoption Act.

“I have championed funding for research into Fragile X Syndrome, a condition not unrelated to autism, that has been remarkable in terms of its success.

“I authored multiple pieces of other legislation that got enacted, ranging from transforming the criminal justice system, to just this week being present at the White House when President Obama signed the Tourism Promotion Act.

“That will actually, in my judgment, make a significant difference for people on the Cape and Islands, because it is designed to attract international visitors to the United States. We’ve lost a huge market share since September 11, because we don’t have a coherent approach to encouraging international visitors.

“On the larger issues, I was an ardent opponent of the Iraq war. I like to think that I helped as chair of the oversight [Subcommittee of Foreign Affairs] to create an environment for Iraqi parliamentarians to express their desire for the American military to leave on a schedule,” he said. “I’ve been extremely involved on the Cuba issue, where we have had an abyssmal policy.”

And of course, he has long championed the Coast Guard and fishing issues; he is a former Coast Guard reservist.

In more local terms, he has sought funding for community health programs for the Islands. He helped arrange financing for the rebuilding of the Mansion House after it burned down.

Surprisingly, he said he was not particularly concerned about the apparent gridlock in Washington and the low esteem in which federal politics is currently held.

“That’s because I read history,” he said. “This is a moment in our history where there is cynicism, but that’s not unknown to us. Thomas Jefferson introduced negative campaigning, against John Adams.”

Of greater concern, Mr. Delahunt said, was that so few people now appeared willing to get involved in politics.

“When I first ran for that one council seat, there was a very strong incumbent and I was one of seven or eight challengers. Today in Quincy, and elsewhere, we have examples of offices that are in search of candidates. And that’s disturbing.

“One would have expected 25 or 30 years ago there would have been a dozen strong candidates running for Ted Kennedy’s seat. There were not.”

Much of that can be put down to the “unseemly and corrosive effect of big money on political campaigning.”

Which brings us to the subject of what might happen to his seat.

“Oh,” he said, “it’s foolish to try to predict in March what’s going to happen in November. I’m hopeful that when it comes to my seat there will be a healthy and robust primary and I will be out there, supporting the party nominee.

“I’m confident we will retain the seat.”

Will he be endorsing any candidate for the Democratic primary?

“I will at this point keep my preferences to myself,” said Congressman Delahunt.