PROVIDENCE — Massachusetts Sen. Edward M. Kennedy, the Democratic Party’s liberal lion, and his son, Rhode Island Rep. Patrick J. Kennedy, will endorse Barack Obama for president today, giving the Illinois senator a new jolt of momentum in his campaign against New York Sen. Hillary Rodham Clinton for the Democratic nomination.

The Kennedy endorsements come in the wake of Obama’s historic landslide victory Saturday in South Carolina’s primary. More important, they arrive eight days before the round of 22 state primaries and caucuses on Feb. 5 that loom as a de facto national primary that could decide whether Clinton or Obama wins the nomination.

The endorsements will be issued at noon at an Obama rally on the Washington, D.C., campus of American University, Patrick Kennedy said in an interview yesterday. He and Edward Kennedy will be joined by Caroline Kennedy, the only surviving child of the late President John F. Kennedy, who only yesterday announced her support of Obama.

Patrick Kennedy said he decided that after eight years of President Bush — and what Democrats assert is a governing style that has mismanaged the Iraq war and the economy, badly botched the response to Hurricane Katrina and dimmed the reputation of the United States abroad — it is time for dramatic change.

“Barack has the power internationally to restore America’s presence in the world. He is the perfect antidote to George Bush,” he said.

“This election is not simply about who can manage government better. This isn’t simply about experience,” the congressman said. “It is about who can restore people’s faith in their government.

“Barack has managed to give so many people some belief that there can be something positive about government. What a great thing that is at a time of such cynicism,” Kennedy said. “I certainly think both Hillary Clinton and John Edwards are fine candidates. Either one can get the job done.

“It is just that there is this extra quality about Barack that has lifted my spirits and the spirits of an entire generation,” he said.

Senator Kennedy was not giving interviews yesterday. But his support had been coveted by both Clinton and Obama, his son said.

Former President Bill Clinton had courted Edward Kennedy personally, as did Hillary Clinton, Patrick Kennedy said. The elderly Kennedy was known by close associates to have been upset about Bill Clinton’s use of what Kennedy considered divisive language and negative campaigning on racial issues in the run-up to Saturday’s South Carolina vote.

Edward Kennedy also appreciated Obama’s strong support last year in the bipartisan quest to shape legislation on immigration reform, a thorny political issue that other presidential candidates avoided.

A Kennedy associate said yesterday that Gregory Craig, a high-powered Washington lawyer who defended Bill Clinton during his Senate impeachment trial in the 1990s, was instrumental in moving Edward Kennedy into Obama’s camp. Craig, a Vermont native, is also a former Kennedy aide who remains close to the senator.

Patrick Kennedy said he did not want to speak publicly about any of the thinking that went into his father’s decision to endorse Obama. But he pointed to the op-ed article by Caroline Kennedy — his cousin and Edward’s niece — that appeared in yesterday’s New York Times.

In an article titled “A President Like My Father,” Caroline Kennedy stated her reasons for supporting the Illinois senator:

“Over the years, I’ve been deeply moved by the people who’ve told me they wished they could feel inspired and hopeful about America the way people did when my father was president. This sense is even more profound today. That is why I am supporting a presidential candidate in the Democratic primaries, Barack Obama.

“My reasons are patriotic, political and personal, and the three are intertwined. All my life, people have told me that my father changed their lives, that they got involved in public service or politics because he asked them to. And the generation he inspired has passed that spirit on to its children. I meet young people who were born long after John F. Kennedy was president, yet who ask me how to live out his ideals.

“Sometimes it takes a while to recognize that someone has a special ability to get us to believe in ourselves, to tie that belief to our highest ideals and imagine that together we can do great things. In those rare moments, when such a person comes along, we need to put aside our plans and reach for what we know is possible.

“We have that kind of opportunity with Senator Obama.”

Caroline Kennedy also pointed to Obama’s opposition to the Iraq war, which Senator Clinton voted in favor of. “When it comes to judgment, Barack Obama made the right call on the most important issue of our time by opposing the war in Iraq from the beginning,” Caroline Kennedy wrote.

Patrick Kennedy said he and his father will campaign around the country for Obama.

Edward Kennedy is particularly revered among the party’s liberal wing, by labor leaders, by advocates for universal health insurance and by minority voters, especially Latinos.

Kennedy said his father will help Obama get a “second look” from party loyalists and “Democratic base voters.”

The far-flung Kennedy clan is not unanimous on the 2008 race. Two of the late Robert F. Kennedy’s children have been campaigning for Clinton. Robert F. Kennedy Jr., a New York lawyer, and Kathleen Kennedy Townsend, a former lieutenant governor of Maryland, have both endorsed the New York senator.

Last year, at the beginning of the Democratic presidential sweepstakes, Patrick Kennedy backed Connecticut Sen. Christopher Dodd, a fellow Providence College alum and longtime confidant of the Kennedys. Dodd dropped out of the race after poor showings in early primaries and caucuses.

Kennedy said he believes Obama has emphasized some of the issues Dodd had, such as getting more Americans involved in public service, establishing better educational and health programs for children, and burnishing the nation’s image abroad with foreign policies more multilateral than the go-it-alone philosophy of the Bush administration.

Every campaign endorsement contains political calculations and personal relationships. One of Obama’s top campaign strategists is David Axelrod, the Chicago-based media consultant who has been close to Patrick Kennedy since he first ran for Congress from Rhode Island’s 1st congressional district in 1994.

One political reason Kennedy cited yesterday is that he, his father and some other Democratic leaders fear that without an expansion of the base of loyal Democratic voters, the 2008 presidential election will be a reprise of the close elections of 2000 and 2004, both won by Mr. Bush.

“We have to get away from relying just on our own base voters,” he said. “Barack has clearly demonstrated in these first primaries and caucuses that he can expand that base.”

While many top Massachusetts Democrats, including Governor Patrick, Sen. John F. Kerry and U.S. Rep. William Delahunt, are backing Obama, Patrick Kennedy becomes the first major Rhode Island Democrat to back the Illinois senator.

All of the other top statewide elected Democrats and party officials are with Clinton. Sen. Jack Reed, who is up for reelection this year, is neutral but Lt. Gov. Elizabeth Roberts, Attorney General Patrick C. Lynch, General Treasurer Frank Caprio, Democratic State Chairman William Lynch and House Speaker William Murphy are all behind Clinton.

“One of the big questions about Barack is, does he have that foundation of Democratic institutional support needed to win,” Kennedy said. “I think my dad’s support definitely brings strong institutional support to Barack.”

smackay@projo.com