"It was a moment packed with political significance," said CBS senior political correspondent Jeff Greenfield. "Ted and Caroline Kennedy the surviving brother and surviving child of the most revered Democratic President declaring that the torch has been passed."
"I feel change in the air," Kennedy said in a speech salted with scarcely veiled criticism of Obama's chief rival for the nomination, Sen. , as well as her husband, the former president.
"I have marveled at his grit and grace," he said of the man a full generation younger than he is.
Kennedy's endorsement was ardently sought by all three of the remaining presidential contenders, and he delivered it at a pivotal time in the race. A liberal lion in his fifth decade in the Senate, the Massachusetts senator is in a position to help Obama court Hispanic voters as well as rank-and-file members of labor unions, two key elements of the Democratic Party.
He is expected to campaign actively for Obama in the days before a string of delegate-rich primaries and caucuses across 24 states on Feb. 5, beginning later this week in Arizona, New Mexico and California.
The senator made his comments at a crowded campaign rally that took on the appearances of a Kennedy family embrace of Obama, who sat smiling as he heard their praise.
He was introduced by Caroline Kennedy, daughter of the late president, who said Obama "offers that same sense of hope and inspiration" as did her father. Rep. Patrick Kennedy also endorsed Obama from the stage before a boisterous crowd at American University.
"This is more than just politics for me. It is personal," Obama, 46, said when it came time for him to speak. He said he was too young to remember President John F. Kennedy, but that "my own sense of what is possible in this country" stems from what his parents told him of the Kennedys.
In his own remarks, Sen. Kennedy sought one by one to rebut many of the arguments leveled by Obama's critics.
"From the beginning, he opposed the war in Iraq. And let no one deny that truth," he said, an obvious reference to former President Clinton's statement that Obama's early anti-war stance was a "fairy tale."
"With Barack Obama, we will turn the page on the old politics of misrepresentation and distortion.
"With Barack Obama we will close the book on the old politics of race against race, gender against gender, ethnic group against ethnic group, and straight against gay," Kennedy said.
The Massachusetts senator had remained on the sideline of the presidential campaign for months, saying he was friends with Obama, Clinton and former North Carolina Sen. , as well as several Senate colleagues who are no longer in the race.
Lately, according to several associates, Kennedy became angered with what he viewed as racially divisive comments by Bill Clinton. Nearly two weeks ago, he played a personal role in arranging a brief truce between the Clintons and Obama on the issue.
Questioned about Kennedy's endorsement, Hillary Clinton said simply, "We're all proud of the people we have endorsing us."
She also defended herself and her husband against criticism that they had engaged in racial politics and distortion of a rival's record.
"There's been no two people who have stood against that more than we have over many years," she said in a conference call with Arizona reporters.
Kennedy refers only sparingly to his assassinated brothers, John and Robert, in his public remarks, and his endorsement of Obama was cast in terms that aides said was unusually personal.
"There was another time, when another young candidate was running for president and challenging America to cross a new frontier. He faced criticism from the preceding Democratic president, who was widely respected in the party," Kennedy said, referring to Harry S. Truman.
"And John Kennedy replied, 'The world is changing. The old ways will not do. ... It is time for a new generation of leadership.
"So it is with Barack Obama," he added.
Kennedy began his remarks by paying tribute to Sen. Clinton's advocacy for issues such as health care and women's rights. "Whoever is our nominee will have my enthusiastic support," he said.
But he quickly pivoted to a strong endorsement of Obama, whom he said "has extraordinary gifts of leadership and character, matched to the extraordinary demands of this moment in history."
"I believe that a wave of change is moving across America," Kennedy said.
The endorsement may run counter to Obama's image as a change agent, but is also likely to help him among groups that, so far, have been loyal to Clinton, Greenfield said on CBS' The Early Show on Monday.
"The question is, Obama is this transformational guy who's saying 'I can move beyond the old left and right'. Well, Ted Kennedy for many people, pro and con, is the symbol of classic American liberalism. He's been in the Senate since Barack Obama was 15 months old," Greenfield said. "That said, among working class Democrats, among Hispanics, among African Americans, Ted Kennedy is a home run."
Today's endorsement represents a break between the Clintons and the Kennedys, two of the Democratic Party's most powerful families, presidential historian Douglas Brinkley said on The Early Show.
"What makes this, I think, a little bit more of a news story is Ted Kennedy squaring off with Bill Clinton saying, 'I don't like how you dealt with the race issue in South Carolina,'" Brinkley said. "When he was president, remember the Clinton's didn't have a home and they used to spend their summers up in Martha's Vineyard, and Hyannis Port, kind of infiltrating the Kennedy compounds, if you like. All that's over now. It's not just an endorsement by Ted Kennedy. He's getting on the campaign trail; he's going to be trying to bring labor unions, and particularly Hispanics, to Barack Obama."
Also Monday, Obama picked up the endorsement of author Toni Morrison, who once labeled Bill Clinton as the "first black president." Morrison said she has has admired Obama rival Hillary Rodham Clinton for years because of her knowledge and mastery of politics, but cited Obama's "creative imagination which coupled with brilliance equals wisdom."
Morrison said her endorsement had little to do with Obama's race - he is the son of a black father from Kenya and a white mother from Kansas - but rather his personal gifts.
Writing with the touch of a poet in a letter to the Illinois senator, Morrison explained why she chose Obama over Clinton for her first public presidential endorsement.
"In addition to keen intelligence, integrity and a rare authenticity, you exhibit something that has nothing to do with age, experience, race or gender and something I don't see in other candidates," Morrison wrote. "That something is a creative imagination which coupled with brilliance equals wisdom. It is too bad if we associate it only with gray hair and old age. Or if we call searing vision naivete. Or if we believe cunning is insight. Or if we settle for finessing cures tailored for each ravaged tree in the forest while ignoring the poisonous landscape that feeds and surrounds it."