A top Massachusetts Democrat said Saturday that one of Robert F. Kennedy's grandsons is considering carrying on the family's vaunted political tradition by running for the U.S. House of Representatives.

Joseph P. Kennedy III, one of the twin sons of former Rep. Joseph P. Kennedy II, may run this fall if Democratic Rep. William Delahunt decides against seeking re-election in his South Shore and Cape Cod district.

Kennedy, 29, "has been considering it but he hasn't made a decision," said the Democrat, who demanded anonymity to speak about private conversations with the father and son.

The younger Kennedy did not immediately respond to a request for comment. He is a graduate of Stanford University and Harvard Law School who works as a prosecutor in Barnstable County, near his family's Cape Cod compound.

Delahunt has served in Congress since 1997, but Massachusetts incumbents were shocked in January when a little-known Republican state senator, Scott Brown, claimed the U.S. Senate seat held for nearly a half-century by Edward M. Kennedy.

That prompted questions about the endurance of the Kennedy legacy and inspired several local Republicans, including former state Treasurer Joe Malone and state Rep. Jeffrey Perry of Sandwich, to say they are considering running for Delahunt's seat.

Brown not only beat his Democratic opponent, Attorney General Martha Coakley, in Delahunt's district, but he also won the Barnstable precinct where the late senator lived and used to vote.

Delahunt has also been criticized in recent weeks for his handling of a 1986 shooting by Amy Bishop, a University of Alabama professor accused of killing three colleagues this month. At the time, Delahunt was the local district attorney, and he accepted the findings of local and state police that Bishop's shooting of her brother was accidental.

"These are rare opportunities when there is a potential open seat," said Paul Watanabe, a political science professor at UMass-Boston. "He is the Kennedy most talked about in terms of carrying on the family tradition in the U.S. House or U.S. Senate."

"It has significant value in terms of fundraising ability, scaring off potential Democratic and Republican contenders, and it immediately thrusts this congressional race into national attention, rather than just one of 434 other races," Watanbe added.

The uncertain political climate, however, would likely play heavily in any final decision by Kennedy, said Boston College political science professor Marc Landy.

"What is unusual is it could be a real contest, because this contest would not be fought on `the Kennedy tradition.' The issues would really matter in this election. And I can't predict how the voters in that district will respond, and neither can he. And that's the big story: Will a Kennedy enter a race with that much uncertainty?" said Landy.

Before Edward Kennedy died of brain cancer in August, a member of his family had served in Congress since 1946, when his brother, future President John F. Kennedy, won a U.S. House seat. Joseph P. Kennedy II held that seat from 1987 to 1999, but he decided against seeking re-election after an aborted run for governor in 1998.