Sen. Ted Kennedy died shortly before midnight Tuesday at his home in Hyannis Port, Mass., at age 77.
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The man known as the "liberal lion of the Senate" had fought a more than year-long battle with brain cancer, and according to his son had lived longer with the disease than his doctors expected him to.
"We've lost the irreplaceable center of our family and joyous light in our lives, but the inspiration of his faith, optimism, and perseverance will live on in our hearts forever," the Kennedy family said in a statement. "He loved this country and devoted his life to serving it."
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Sen. Edward Moore Kennedy, the youngest Kennedy brother who was left to head the family's political dynasty after his brothers President John F. Kennedy and Sen. Robert F. Kennedy were assassinated.
Kennedy championed health care reform, working wages and equal rights in his storied career. In August, he was awarded the Presidential Medal of Freedom -- the nation's highest civilian honor -- by President Obama. His daughter, Kara Kennedy, accepted the award on his behalf.
Sen. Edward M. Kennedy, known as Ted or Teddy, was diagnosed with a malignant brain tumor in May 2008 and underwent a successful brain surgery soon after that. But his health continued to deteriorate, and Kennedy suffered a seizure while attending the luncheon following President Barack Obama's inauguration.
For Kennedy, the ascension of Obama was an important step toward realizing his goal of health care reform.
At the Democratic National Convention in August 2008, the Massachusetts Democrat promised, "I pledge to you that I will be there next January on the floor of the United States Senate when we begin the great test."
Sen. Kennedy made good on that pledge, but ultimately lost his battle with cancer.
Kennedy was first elected to the Senate in 1962, at the age of 30, and his tenure there would span four decades.
A hardworking, well-liked politician who became the standard-bearer of his brothers' liberal causes, his career was clouded by allegations of personal immorality and accusations that his family's clout helped him avoid the consequences of an accident that left a young woman dead.
But for the younger members of the Kennedy clan, from his own three children to those of his brothers JFK and RFK, Ted Kennedy -- once seen as the youngest and least talented in a family of glamorous overachievers -- was both a surrogate father and the center of the family.
And certainly it was Ted Kennedy who bore many of the tragedies of the family -- the violent deaths of four of his siblings, his son's battle with cancer, and the death of his nephew John F. Kennedy Jr. in a plane crash.
Ted Kennedy (1932-2009) 
United States Senator Ted Kennedy, a Democrat from Massachusetts died just before midnight on August 25, 2009, at his home in Hyannis Port at age 77. He was the brother of American President John F. Kennedy and  U.S. Senator Robert F. Kennedy.

On May 20, 2008, Kennedy was diagnosed with a brain tumor, and was released from Massachusetts General Hospital on May 21.

He was born Edward Moore Kennedy on February 22, 1932, in Boston. He had been a senator since 1962.

Kennedy is survived by his wife Victoria Reggie Kennedy, three children, two step-children, a sister — Jean Kennedy Smith, many nieces and nephews and several grandchildren.

The Kennedy family released a statement saying, "Edward M. Kennedy — the husband, father, grandfather, brother and uncle we loved so deeply — died late Tuesday night at home in Hyannis Port. We’ve lost the irreplaceable center of our family and joyous light in our lives, but the inspiration of his faith, optimism, and perseverance will live on in our hearts forever. We thank everyone who gave him care and support over this last year, and everyone who stood with him for so many years in his tireless march for progress toward justice, fairness and opportunity for all. He loved this country and devoted his life to serving it. He always believed that our best days were still ahead, but it’s hard to imagine any of them without him."

Kennedy was the second-most-senior current member of the Senate, after Democratic President ''pro tempore'' Robert Byrd of West Virginia, and the third-longest-serving senator of all time, behind Byrd and Republican Senator Strom Thurmond of South Carolina. Kennedy was known as "The Lion of the Senate," for his long tenure and influence in the Senate. Throughout his career, Kennedy and his staff wrote more then 300 bills that were enacted into law.

Because of Kennedy's death, the Democratic Party has lost their sixty-seat supermajority in the Senate. His successor will be chosen in a special election within 160 days. Prior to his death, Kennedy appealed to Democratic Massachusetts Governor Deval Patrick and the Massachusetts legislature to change state law regarding Senate vacancies, so that a temporary senator could be appointed pending a special election and a vote in favor of a health-care bill would not potentially be lost.  This law had been changed in 2004 to prevent Republican then-Governor Mitt Romney from appointing a replacement for Democratic Senator John Kerry, had he won the 2004 presidential election.