WASHINGTON — Sen. Edward M. Kennedy was a Democrat's Democrat, so much so that he became a rallying point for those in his party and an object of derision for Republican opponents.
Yet his affability and capability to span the partisan divide on an array of legislative matters prompted an outpouring of condolences from those in the GOP as well as the Democratic Party following his death Tuesday at age 77 from brain cancer .
"An important chapter in our history has come to an end," said President Barack Obama, who called Kennedy a colleague, counselor and friend and "the greatest United States senator of our time ."
"Even though we knew this day was coming, we awaited it with no small amount of dread," Obama said, speaking outside a beach house where he's vacationing with his family on Martha's Vineyard. "For his family, he was a guardian. For America, he was a defender of a dream."
Former President George H.W. Bush expressed sympathies from members of the Republican Party.
"While we didn't see eye to eye on many political issues through the years, I always respected his steadfast public service," he said in a statement.
Bush's son, former President George W. Bush, said he was pleased to work with Kennedy on legislation for improving public schools, immigration rule and mental illness care.
"In a life filled with trials, Ted Kennedy never gave in to self-pity or despair," the younger Bush said.
'I will miss him'
The widow of another Republican president, Ronald Reagan, also ofered warm words.
"Given our political differences, people are sometimes surprised by how close Ronnie and I have been to the Kennedy family," Nancy 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," she said, adding, "I considered him an ally and a dear friend. I will miss him."
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Ronald Reagan died in June 2004 of complications from Alzheimer's disease.
Sen. John McCain, R.-Ariz., who ran for president against Obama, praised Kennedy's willingness to reach out to those who did not share all of his political convictions.
"Many of his fellow senators, Republicans and Democrats, liberals and conservatives, will note today that Ted was sincerely intent on finding enough common ground among us to make progress on the issues of our day," McCain said.
The Senate will seem a "less interesting place in the knowledge that his booming voice, fueled by his passion for his convictions, will never encourage or assail or impress us again," McCain added.
Former Democratic President Bill Clinton called Kennedy "one of the most influential leaders of our time.
"Hillary and I will always be grateful for the many gestures of kindness and generosity he extended to us, for the concern he showed for all the children and grandchildren of the Kennedy clan, and for his devotion to all those in need whose lives were better because he stood up for them," Clinton said.
Secretary of State Hillary Rodham Clinton, whose White House run was dealt a blow last year by Kennedy's endorsement of Obama, praised Kennedy for championing "women and families, health care, education, civil rights and the environment.
"His legacy will live on in the hearts and minds of millions of Americans who are freer, healthier and more prosperous because of his efforts," she said. "As he said, the work goes on, the cause endures, the hope still lives, and the dream shall never die."
'Best friend in the Senate'
For some members of Kennedy's own party, the loss was deeply personal.
"My heart and soul weeps at the loss of my best friend in the Senate, my beloved friend," said Sen. Robert C. Byrd of West Virginia. Byrd and Strom Thurmond were the only members of the Senate to have served longer than Kennedy, who had represented Massachusetts for more than 46 years.
Video: Remembering Ted Kennedy "Senator Kennedy and I both witnessed too many wars in our lives, and believed too strongly in the Constitution of the United States to allow us to go blindly into war. That is why we stood side by side in the Senate against the war in Iraq," he added.
For the governor of California, Kennedy's death was a family matter.
Arnold Schwarzenegger, whose wife, Maria Shriver, was Kennedy's niece, said in a statement: "He was known to the world as the Lion of the Senate, a champion of social justice, and a political icon. Most importantly, he was the rock of our family: a loving husband, father, brother and uncle."
Kennedy’s death came just two weeks after that of Shriver’s mother, Eunice Kennedy Shriver , one of the senator’s siblings.
Vice President Joe Biden fought tears as he spoke about his friend and colleague of many decades in the Senate.
“I truly, truly am distressed by his passing,” Biden said. “Teddy spent a lifetime working for a fair and more just America. For 36 years, I had the privilege of going to work every day and sitting next to him and being witness to history. ... He restored my sense of idealism.”
Former Vice President and ex-Sen. Al Gore called Kennedy “a champion for those Americans who had no voice — the sick, the disabled, the poor, the under-privileged.”
John Boehner, the House Republican leader, said that he counted Kennedy as a friend despite being on the opposite side of the political divide.
"While there were few political issues on which he and I agreed, our relationship was never disagreeable, and was always marked by good humor, hard work, and a desire to find common ground," Boehner said.
Former Massachusetts Gov. Mitt Romney, a 2008 GOP presidential contender, recalled losing to Kennedy in a 1994 Senate race. Nonetheless, the two joined forces in 2006 to help pass a universal health insurance law in Massachusetts.
"The last son of Rose Fitzgerald and Joseph Kennedy was granted a much longer life than his brothers, and he filled those years with endeavor and achievement that would have made them proud," Romney said, recalling the assassinations of John F. Kennedy and Robert Kennedy, as well as the World War II death of Joseph Kennedy.
"In 1994, I joined the long list of those who ran against Ted and came up short. But he was the kind of man you could like even if he was your adversary," Romney added.
Republican Sen. Orin G. Hatch of Utah called Kennedy a "treasured friend."
Hatch said that although the two disagreed on most issues, "once in a while we could actually get together and find the common ground, which is essential in passing legislation."
Former Republican Sen. Bob Dole, said: "Ted and I served together for 35½ years, 27½ of those in the U.S. Senate, where we worked together on many important pieces of legislation, including the Martin Luther King Holiday Bill, the Americans with Disabilities Act and Social Security amendments. He is the hardest working senator I met. He was always prepared.
"He was a strong ally if you were in agreement but a formidable opponent when he had a different view. Though he had his own philosophy, he always reached across the aisle for a bipartisan solution on issues that mattered to the American people and he could grasp where those compromises could be found better than anyone."
Health care reform
Senate Majority Leader Harry Reid, D-Nev., called Kennedy the "patriarch" of the party and promised that Congress 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. “The liberal lion’s mighty roar may now fall silent, but his dream shall never die.”
Kennedy's junior colleague, Sen. John Kerry, a Massachusetts Democrat, lauded him as a "larger than life" presence.
"He taught us how to fight, how to laugh, how to treat each other, and how to turn idealism into action, and in these last 14 months, he taught us much more about how to live life, sailing into the wind one last time," Kerry said.
Former President Jimmy Carter, who beat out Kennedy for the 1980 Democratic presidential nomination, praised Kennedy during a visit Wednesday to the West Bank town of Ramallah.
"The courage and dignity he exhibited in his fight with cancer was surpassed only by his lifelong commitment and service to his country."
Mourned in 'every continent'
British Prime Minister Gordon Brown said Kennedy would be mourned in "every continent."
Video: Allies from both sides of political aisle remember Kennedy "He is admired around the world as the senator of senators," Brown told Britain's Press Association.
"He led the world in championing children's education and health care, and believed that every single child should have the chance to realize their potential to the full.
"I am proud to have counted him as a friend and proud that the United Kingdom recognized his service earlier this year with the award of an honorary knighthood."
Tony Blair, the former British prime minister, praised Kennedy's "passionate commitment" to the Northern Ireland peace process.
"Senator Kennedy was a figure who inspired admiration, respect and devotion, not just in America but around the world," Blair said.
"He was a true public servant committed to the values of fairness, justice and opportunity."
In Ireland, where photographs of the Kennedy family adorn homes and hundreds claim to be distant relations of the dynasty, Kennedy is largely known as JFK's brother but also a power broker who mobilized Irish Americans and their political views on Northern Ireland.
"He lived to see two great chasms bridged, between Catholic and Protestant in Northern Ireland and between black and white in his own United States," former Irish Prime Minister Bertie Ahern said. "These achievements, which were the dreams imagined by his brothers in his youth, were the legacy of a long life and of a good and great man."
More on: Edward Kennedy
NBC News and The Associated Press contributed to this report.