Republican Scott Brown was sworn in Thursday as a U.S. senator from Massachusetts, officially bringing to a close the late Ted Kennedy's long tenure in the Senate and as a national political figure.  Kennedy died last August, and Brown was elected last month to replace him. 

Republican Scott Brown took his place in the U.S. Senate after the official swearing-in by Vice President Joe Biden. "If the senator-elect will now present himself at the desk, the chair will now administer the oath of office," said Biden.

Brown's seat was held for 46 years by the late Senator Ted Kennedy, who died last August after a battle with brain cancer.

Growing up in Massachusetts, it was hard to remember a time when a Kennedy was not dominating state politics and making national political headlines as well.

Beginning of Kennedy era

In 1946, war hero John F. Kennedy won a House seat in Massachusetts, and six years later was elected to the Senate.

In 1960, John Kennedy set his sights on higher office. "I am announcing today my candidacy for the presidency of the United States.  I plan to enter the New Hampshire primary contest," he said.

Kennedy won the 1960 election.  A family friend held his former Senate seat until 1962 when his youngest brother, Ted Kennedy, was old enough to run.

Ted Kennedy won his first Senate election in 1962.  Two years later, his brother Robert was elected to the Senate from New York.

After Robert Kennedy's assassination while running for president in 1968, Ted Kennedy recommitted himself to a life of public service.

"Like my three brothers before me, I pick up a fallen standard.  Sustained by their memory of our priceless years together, I shall try to carry forward that special commitment to justice, to excellence, to courage, that distinguished their lives," he said.

Ted Kennedy harbored presidential dreams of his own.  But those hopes were dashed following a 1969 car accident in Massachusetts in which a young woman died and Kennedy's reputation suffered because of his erratic behavior after the accident.

Kennedy did challenge President Jimmy Carter for the 1980 Democratic nomination, but was unable to rally voters to his cause. "For me, a few hours ago this campaign came to an end," he said. "For all those whose cares have been our concern, the work goes on, the cause endures, the hope still lives and the dream shall never die!"

Ted Kennedy devoted the rest of his political career to fighting for liberal causes in the U.S. Senate, including health care, civil rights and helping the poor.

His endorsement of candidate Barack Obama in the 2008 presidential campaign helped then-Senator Obama defeat rival Hillary Clinton for the party's presidential nomination.

Though ill with cancer, Ted Kennedy spoke on Barack Obama's behalf at the Democratic Party convention in Denver in 2008. "I have come here tonight to stand with you to change America, to restore its future, to rise to our best ideals and to elect Barack Obama president of the United States," he said.

End of Kennedy era

Kennedy's death last year and the election of Republican Scott Brown in January signaled the end of an era in U.S. politics that featured the three Kennedy brothers in prominent roles, from the early 1950's right up until 2009.

Kennedy's successor in the Senate, Republican Scott Brown, paid tribute to his legacy in his victory speech election night. "Senator Ted Kennedy was a tireless worker and a big-hearted public servant, and for most of his lifetime was a force like no other in this state," he said.

Senate historian Donald Ritchie says Ted Kennedy's political legacy will have a prominent place right alongside those of his brothers, John and Robert.

"Well, he is clearly one of the giants of the Senate, certainly of his era in the Senate," he said. "He had time to get a lot of major legislation through, and he was famous for building the coalitions that were necessary to enact legislation that will affect American life for decades, if not longer."

The late Senator Kennedy's son Patrick is a congressman from Rhode Island, and many other younger Kennedy's have become active in various causes, though not necessarily elective politics.

But political experts say the younger generation of Kennedy's will have a difficult time matching the national political impact of John, Robert and Ted Kennedy.