BOSTON — When Barack Obama's presidential prospects sagged, Sen. Edward Kennedy lifted the candidate with a coveted endorsement.

When brain cancer kept the Massachusetts Democrat from delivering his stepdaughter's college commencement address, Obama left the campaign trail and stood in for his then-Senate colleague.

And when Obama made one of the most closely watched decisions of his young presidency — the type of puppy for his daughters — it was Kennedy who gave him "Bo," a Portuguese water dog like the pair that have been a fixture in Kennedy's Capitol Hill offices.

With Kennedy now at his vacation home in Hyannis Port on Cape Cod and Obama setting off on his weeklong stay on nearby Martha's Vineyard, there's speculation the president may come see the ailing senator.

A visit could provide a rallying point for Democrats as Obama seeks to achieve one of Kennedy's career goals: overhauling the nation's health insurance system to provide near-universal coverage.

It also would show anew the close relationship between the first African-American president and the last vestige of the Camelot White House era.

Despite a gulf in age, race and life experience, the 48-year-old Obama and the 77-year-old Kennedy have built a personal bond evident in the tribute the president paid Kennedy and his assassinated brothers, President John F. Kennedy and Sen. Robert F. Kennedy, before he signed the Edward M. Kennedy Serve America Act into law in April.

"I want all Americans to take up that spirit of the man for whom this bill is named; of a president who sent us to the moon; of a dreamer who always asked, 'Why not?' — of a younger generation that carries the torch of a single family that has made an immeasurable difference in the lives of countless families," Obama said.

Those who know both men find the relationship understandable, despite the age difference.

"He is the kind of president that Kennedy can relate to," said Robert Shrum, who helped drafted the senator's famous 1980 Democratic National Convention concession speech and remains a close personal friend.

"He's trying to do very, very big things. He's appealed to people's idealism. He's appealed to their notion of service, things that have been touchstones of Kennedy's life," Shrum said.

Capitol Hill aides say the two men were not especially close during Obama's first 18 months in the Senate, which began in 2005.

They shared a mutual bond in opposing the Iraq War, but there was little more than a collegial relationship.

The turning point came in 2006, when Obama visited Kennedy to ask whether he should run for president.

"Your time only comes once, and this is your time," Kennedy told Obama, according to a Kennedy aide who spoke on condition of anonymity to recount a private conversation.