“It is time again for a new generation of leadership,” Sen. Edward Kennedy (D-Mass.) declared in a midday press conference in Washington D.C. today. “It is time now for Barack Obama,” added Kennedy, in endorsing his Senate colleague from Illinois for president of the United States. Implicitly addressing Bill and Hillary Clinton’s main charge against Obama — that he lacks the experience to be president — Kennedy declared him “ready to be president on day one.”

Kennedy was introduced by his niece (and the daughter of the late President John F. Kennedy), Caroline Kennedy, who endorsed Obama yesterday in an op-ed in the Sunday New York Times. U.S. Rep. Patrick J. Kennedy (D-R.I.), the son of the Massachusetts senator, joined his father and cousin on the podium at American University today in endorsing Obama.

“The coveted endorsement is a huge blow to New York Senator Hillary Clinton, who is both a senatorial colleague and a friend of the Kennedy family,” says the Boston Globe. “In a campaign where Clinton has trumpeted her experience over Obama’s call for hope and change, the endorsement by one of the most experienced and respected Democrats in the Senate is a particularly dramatic coup for Obama,” adds Globe staff writer Susan Milligan.

Bill and Hillary Clinton have been courting the brother and daughter of President John F. Kennedy for months. The Clinton camp’s response — pointing to the endorsements Hillary has received from children of the late senator from New York who was attorney general in his brothers administration, Kathleen Kennedy Townsend (a former Democratic lieutenant governor of Maryland) and Robert F. Kennedy, Jr., a prominent environmental activist) — has an air of desperation.

What strikes me as particularly significant about Ted Kennedy’s endorsement of Barack Obama is its timing and impetus. “Associates [of Kennedy’s] said had grown furious at the tone of the presidential campaign, including the words and actions of former President Bill Clinton,” reports Jeff Zeleny in today’s New York Times.

Reports suggest that Bill Clinton and Ted Kennedy had an angry exchange when the latter called the former to inform him that he was endorsing Obama. But if there is such a thing as ‘boomerang karma,’ this seems to be a perfect example: the racially divisive campaign that the Clintons waged against Obama in South Carolina so outraged Ted Kennedy that it seems to have prompted him to break his pledge of neutrality and throw his support to Obama.

Endorsements rarely alter primary election outcomes, but this trio of endorsements may have some impact. “In the hierarchy of endorsements, Kennedy coming out for Obama falls into the category of ’symbolic endorsement,’ the most coveted of all because it is not simply the typical pat on the back and photo-op, but rather it signifies something larger about a candidate,” Chris Cillizza writes today on his blog page on the Washington Post site. “The endorsement by the senior senator from Massachusetts was widely seen as important for Obama because it gives him the imprimatur of a major leader of the Democratic establishment,” Cillizza adds.

“While endorsements don’t usually matter much, Edward Kennedy’s does,” says Mark Halperin on The Page, Time Magazine’s campaign blog, because:

1. He has a huge following with Hispanics, a big deal in California and other Super Tuesday states, and one of Obama’s weaknesses.
2. The symbolic Kennedy family thing — the ultimate message of change, viability, Democratic legitimacy, and youthful excitement.
3. The national press will be obsessed with the story for days and days to come, with no downside for Obama; the local press coverage when Kennedy travels for Obama will be ginormous.
4. It sends a message to other senators and superdelegates that it is OK to be for Obama — they don’t have to be afraid of the Clintons.
5. He has a huge following among working-class, traditional Democrats, one of Obama’s weaknesses.
6. He has a huge following among union households, another of Obama’s weaknesses.