Sen. Edward M. Kennedy, the Massachusetts Democrat and icon of American liberal politics who was the last surviving brother of a legendary political family, died late last night at his home in Hyannis Port, Mass., his family announced. He was 77.

Kennedy had been in declining health since suffering a seizure in May 2008. Subsequent tests determined that he had a malignant brain tumor.

His family announced his death in a brief statement released last night.

"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 statement said. "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."

President Obama last night said the U.S. has lost "the greatest United States senator of our time."

He called Kennedy "a great leader" and praised his work to advance the civil rights, health and economic well-being of all Americans.

Kennedy had not been to the Capitol since April, missing the passage in June of his groundbreaking measure to regulate tobacco. In July, he could not participate in the drafting of health care legislation.

Senate Democratic Leader Harry Reid says both the Kennedy family and the Senate have "lost our patriarch." Reid promised that Congress, while mourning Kennedy's loss, would renew the push for the cause of Kennedy's life, health care reform.

"Ted Kennedy's dream was the one for which the Founding Fathers fought and for which his brothers sought to realize," Reid said in a statement. "The liberal lion's mighty roar may now fall silent, but his dream shall never die."

A popular figure on both sides of the aisle in the Senate, Kennedy electrified his colleagues in July 2008 when he appeared briefly to vote on a measure to stave off a cut in Medicare fees to doctors who treat seniors, military personnel and their families and others. The measure passed on a 69-30 vote.

Kennedy was greeted with a wild reception from the party faithful in August 2008 on the first night of the Democratic National Convention in Denver. He addressed the gathering in a strong, steady voice, predicting that "this November, the torch will be passed to a new generation of Americans," a reference to Illinois Sen. Barack Obama. Kennedy's endorsement of Obama in January 2008 was credited as an important validation of the senator's bid to win the nomination against Sen. Hillary Rodham Clinton of New York.

As the standard-bearer for the liberal wing of the Democratic Party, the square-jawed "Ted" or "Teddy" Kennedy believed in government's ability to help solve people's problems, and over the decades he learned how to wield power in the Senate to move the government in that direction. He found numerous ways to work with Republican administrations and senators to fashion significant legislation on issues he cared deeply about.

Kennedy's death leaves Hawai'i Sen. Daniel K. Inouye as the second most-senior member of the Senate, behind Robert Byrd of West Virginia.

"America lost a great patriot and a great leader. I lost a good friend. America mourns Ted Kennedy's passing," Inouye said in a statement last night.

Hawai'i's other U.S. senator, Daniel Akaka, issued a statement that said: "Ted Kennedy was a dear, dear friend. For years, I sat next to him on the Senate floor. He was a passionate member of the U.S. Senate, always trying to help other people, especially those less fortunate. He envisioned a day when all Americans had access to quality education and health care. He joined me in Hawai'i many times and I can't thank him enough for his work. He was the Lion of the Senate. My prayers are with his family."

Hawai'i Congressman Neil Abercrombie said in a statement: "We have lost one of our nation's greatest progressive leaders ... but we have made tremendous gains through his compassion, courage and vision. Senator Kennedy was a life-long advocate for those who needed a voice in the halls of Congress, working tirelessly to advance America's social and economic progress and to raise the quality of life for all of us.

"We have lost him at a critical crossroads in the national debate on health care — an issue that he cared about deeply. It will be a fitting tribute that we pass a health care bill to honor his work and legacy."

Kennedy became a national figure after his brothers, President John F. Kennedy and presidential hopeful Sen. Robert F. Kennedy, were assassinated in the 1960s. Many Americans still yearned for a Kennedy who could occupy the White House, and they looked to the youngest of the Kennedy brothers to fulfill those hopes.

But his public image and political fortunes suffered an indelible stain on July 18, 1969, when he drove his Oldsmobile off a bridge into the water on Chappaquiddick Island in Massachusetts. He survived without serious injury, but his female passenger, 28-year-old Mary Jo Kopechne, died. In a lapse of judgment that was never fully explained, Kennedy sought the help of friends and advisers and delayed reporting the accident to police for 10 hours.

Nothing he did afterward could wipe out the public memory of that lapse.

In 1980, apparently believing that enough time had passed, he launched a fierce primary challenge against unpopular President Jimmy Carter that roiled the Democratic Party. Republican Ronald Reagan defeated Carter handily in the general election.

Once asked what his best quality was as a legislator, he answered: "Persistence."

His affability and capability to span the partisan divide on an array of legislative matters prompted an outpouring of condolences.

"Given our political differences, people are sometimes surprised by how close Ronnie and I have been to the Kennedy family," Nancy Reagan, widow of Republican President Reagan, said in a statement from Los Angeles. "But Ronnie and Ted could always find common ground, and they had great respect for one another.

"In recent years, Ted and I found our common ground in stem cell research, and I considered him an ally and a dear friend. I will miss him."

Her husband died in June 2004 of complications from Alzheimer's disease.

California Gov. Arnold Schwarzenegger, whose wife, Maria Shriver, was Kennedy's niece and who came to politics after careers as a bodybuilder and actor, credited Kennedy with helping him in his current role.

"I have personally benefited and grown from his experience and advice, and I know countless others have as well," he said. "Teddy taught us all that public service isn't a hobby or even an occupation, but a way of life and his legacy will live on."

Former Massachusetts Gov. Mitt Romney, a 2008 GOP presidential contender, recalled losing to Kennedy in a 1994 Senate race.

"But he was the kind of man you could like even if he was your adversary," Romney said.

Edward Moore Kennedy was born Feb. 22, 1932, in Brookline, Mass. The youngest of nine children, he was the son of Joseph P. Kennedy Sr., a self-made millionaire who descended from Irish immigrants and rose to become the U.S. ambassador to Britain. Ted's mother, Rose, was the daughter of John F. "Honey" Fitzgerald, a former Boston mayor.

Though Kennedy's life was privileged, it was filled with tragedy almost from the beginning. When he was 12, his brother Joe Jr., a Navy pilot, was shot down over England during World War II. When he was 16, one of his sisters, Kathleen, died in a plane crash. Earlier, when he was 9, his mentally disabled sister Rosemary was sent to an institution; she died in 2005.

Kennedy went to Harvard University but as a freshman was expelled after having a friend take a Spanish exam for him. He enlisted in the Army, rising to private first class and winning an honorable discharge in 1953. He was accepted back at Harvard and graduated in 1956.

Kennedy was in Washington on Nov. 22, 1963, when he received word that the president had been shot to death in Dallas. It was the beginning of another string of tragedies for the family.

On June 19, 1964, a private plane flying Kennedy from Washington to Springfield, Mass., crashed, killing an aide and the pilot. Kennedy suffered a broken back, forcing him to campaign for his first full Senate term from a hospital bed. He won the election with almost 75 percent of the vote.

Then, on June 5, 1968, his brother Robert, then a New York senator, was shot at the Ambassador Hotel in Los Angeles; he died the next day.

Kennedy seemed to reach his full potential in his continued efforts to champion the poor, abused and deprived. When his party was out of power in the Senate, Kennedy was able to get things done. For example, in 1996, working in tandem with Sen. Nancy Kassebaum, R-Kan., he pushed through legislation that guaranteed Americans the right to buy health insurance and limited the length of time that an insurer could deny coverage for a specific "pre-existing" medical condition.

Also in 1996, Kennedy spearheaded legislation to raise the minimum wage. In 1999, he sponsored and passed legislation to allow the handicapped to work without losing Medicaid health benefits. And he was one of the Senate authors of the "patients' bill of rights."

Kennedy did not attend the funeral for his sister, Eunice Kennedy Shriver, who died Aug. 11, or a White House ceremony during which he was awarded a Presidential Medal of Freedom.

But in the end, he would live decades longer than his brother John, who died at 46, and his brother Robert, who died at 42.

Besides his wife and his son, Edward Jr., Kennedy is survived by his daughter, Kara Kennedy Allen, and another son, Patrick, who is representing Rhode Island in the House.