WASHINGTON (AP) — Sen. Edward M. Kennedy will be a tough act to follow, even for the Kennedys. His death, coupled with the decision by family members not to seek the seat he held for nearly five decades, has prompted predictions that the family’s long-running political dynasty is over.

There’s talk the Kennedy political bloodlines are running thin. Some say the younger brood lacks the grit and zest for political combat that drove the liberal Democrat to become one of the leading politicians of the last 40 years.

Yet it’s probably too early to write off one of America’s most powerful and popular families. A new generation of Kennedys, many of whom are active in humanitarian and political causes, could emerge to extend the dynasty.

Stephen Hess, author of “America’s Political Dynasties,” said such dynasties often ebb and flow. And while no obvious family successors to the late senator are apparent, there is a pool of about two dozen Kennedy cousins. Some of them could go on to make their mark in national politics.

“To be a dynasty, one of the things that is very helpful, almost necessary, is a lot of children,” said Hess, who has been a consultant, adviser and speechwriter to presidents dating back to Dwight D. Eisenhower. “That name, or that legacy, is going to inspire some of them to go into elective politics, particularly since it obviously gives them an advantage.”

Hess noted that back in the 1960s, few were predicting Ted Kennedy would become the family’s standardbearer after his two older brothers, John, the president, and Robert, the former attorney general turned senator, were slain.

“He was not expected to be the leading figure of his generation,” Hess said. “Not only was he, tragically, because of the death of his brothers, but more importantly because he stayed in the Senate and had a remarkable record of achievement.”

Some Democrats hope the late senator’s eldest son, Edward Kennedy Jr., steps up. The Connecticut attorney, 48, said he’s considering following in his father’s footsteps in politics but has no immediate plans to do so. He has two children, ages 11 and 15.

“I’m told one day my children will not want to hang out with me,” Kennedy said last month after his speech to a labor convention in New Haven, Conn. “Maybe at that time I’ll consider that.”

The younger Kennedy, who lost a leg to cancer at age 12, delivered a moving tribute at his father’s funeral last August, recalling how his dad encouraged him to climb a snowy hill to sled. He said it was a poignant lesson in overcoming painful losses. Kennedy founded an investment firm, the Marwood Group, in New York City and is an advocate for the disabled.

Former six-term Massachusetts congressman Joe Kennedy, 57, the eldest son of Robert Kennedy, recently balked at running for his uncle’s Senate seat. His congressional background and his work running Citizens Energy Corp., which provides discounted heating oil to low-income families, could help if he returns to politics.

However, his public image was hurt in 1997 after his former wife, Sheila Rauch Kennedy, published a book accusing him of trying to bully her into agreeing to an annulment of their marriage.

There’s also been speculation that one of Joe Kennedy’s two sons, Joseph Kennedy III, could seek his father’s old House seat if the current holder, Democratic Rep. Michael Capuano, wins the special election to replace Ted Kennedy in Massachusetts.

Kathleen Kennedy Townsend, the eldest of Robert Kennedy’s 11 children, was lieutenant governor of Maryland, but her 2002 gubernatorial bid sputtered.

Rhode Island congressman Patrick Kennedy, the youngest son of Ted Kennedy, has used his struggles with depression and substance abuse to champion better care for the mentally ill, but there are no signs he’s eager for a Senate seat.

Patrick Kennedy is also embroiled in a dispute with his church. Rhode Island’s Roman Catholic Bishop Thomas Tobin said Sunday that he’s asked Kennedy not to receive Holy Communion because of the congressman’s support of abortion rights.

The children of the late Eunice Kennedy Shriver, founder of the Special Olympics and one of Ted Kennedy’s siblings, have long been active in humanitarian causes.

Timothy Shriver is chairman and CEO of Special Olympics. Maria Shriver is California’s first lady. Anthony Paul Shriver founded Best Buddies International to help people with intellectual disabilities. Mark Shriver, a former member of the Maryland House of Delegates, works for Save the Children.

Even if some younger Kennedys jump into politics, it’s unlikely they could match the success of their elders, said Jeffrey Berry, a Tufts University political science professor.

“That’s such a high standard that’s almost impossible to meet unless one becomes president or a United States senator,” Berry said. “So that’s a pretty tall mountain to climb.”

Hess said he would not be surprised if the new Kennedy generation focuses on humanitarian pursuits over elective politics. It remains to be seen if the younger Kennedys could have the same impact on national politics, Hess said.

“A name, a great brand like that, is usually worth one step up on the political ladder,” he said. “Then you are on you own.”