"For five decades, virtually every major piece of legislation to advance the civil rights, health and economic well-being of the American people bore his name and resulted from his efforts," Obama said of the Massachusetts senator, who died Tuesday at his home on Cape Cod, Mass., after a yearlong struggle with brain cancer. He was 77.
A senior administration official said Obama was told of Kennedy's death shortly after 2 a.m. Wednesday, and spoke with the senator's widow, Victoria, around 2:25 a.m.
The president, vacationing at Martha's Vineyard off the Massachusetts coast, thanked Kennedy for "his wise counsel" during Obama's short time serving as a senator from Illinois.
"I cherished his confidence and momentous support in my race for the presidency," Obama added. Kennedy and his niece Caroline shook up the Democratic establishment in January 2008 when they endorsed Obama over Hillary Rodham Clinton for the party's nomination for president.
Exactly one year before his death, Kennedy gave a rousing speech at the Democratic National Convention in Denver, where Obama accepted the presidential nomination. Kennedy returned to the Capitol in January to see Obama sworn in as the nation's first black president, but suffered a seizure at a celebratory luncheon afterward.
He was away from the Senate for much of this year, leading to speculation about the impact of his absence on Obama's health care proposals. Still, Obama said, "even as he waged a valiant struggle with a mortal illness, I've profited as president from his encouragement and wisdom."
"An important chapter in our history has come to an end," Obama said. "Our country has lost a great leader, who picked up the torch of his fallen brothers and became the greatest United States Senator of our time."