Obama's victory in the Maine caucuses follow on the heels of his Saturday sweep in which he won Louisiana's primary contest as well as caucuses in the states of Washington and Nebraska.
His winning margins ranged from substantial to crushing. In Maine, he led 59 percent to 40 percent with 99 percent of the precints reporting. In Louisiana, Obama defeated Clinton, 57 percent to 36 percent. He won in Nebraska by a 68 percent to 32 percent margin and in Washington 68 percent to 31 percent.
Obama's victory in Maine -- and the ease with which it came -- actually exceeded expectations, even though he swept the caucuses held on Super Tuesday. Clinton had the backing of the state's governor, John Baldacci, and its proximity to New Hamsphire and Massachusetts, both of which Clinton has already won this year, led some analysts to expect a close race.
Even Obama's own campaign said they didn't expect to win Maine, according to a document the campaign said was accidentally leaked earlier in the week.
In the delegate chase, Obama has pulled ahead of Clinton, even when the support of uncommitted super delegates is figured in. According to CBS News estimates as of Sunday night, Obama holds a razor-thin lead with 1,134 delegates overall to 1,131 for Clinton. Click here for the latest state-by-state delegate count.
The results in Maine came in the wake of a shake-up on the Clinton campaign. Sunday afternoon, Clinton campaign manager Patti Patti Solis announced she was stepping down from that post. She will be replaced by senior advisor and longtime Clinton confidant Maggie Williams.
Campaign spokesman Mo Elleithee said Solis Doyle was "not asked to step down," reports CBS News' Fernando Suarez. Elleithee said the change in leadership was not due to this weekend's losses.
In a letter to campaign staff, Solis Doyle wrote, "I have been proud to manage this campaign, and prouder still to call Hillary my friend for more than sixteen years. I know that she will make a great President."
"This has already been the longest Presidential campaign in the history of our nation, and one that has required enormous sacrifices from all of us and our families," she continued.
Democrats in 420 Maine towns and cities were deciding Sunday how the state's 24 delegates will be allotted at the party's national convention in August. Despite the weather, turnout was "incredible," party executive director Arden Manning said.
Organizers had expected heavy participation at the caucuses, but up to 8 inches of snow and Arctic cold were expected when many of the gatherings were scheduled. Even so, Democrats started Sunday with more than 4,000 absentee ballots in hand.
State-By-State Delegate Count
Manning said the weather would not hurt turnout. In Bangor, the caucus started late because so many people showed up that they were lined up outside the door, he said.
In Portland, waterlogged Democrats carrying "Obama" and "Hillary" signs waited to get into the citywide caucus at Portland High School in separate lines that snaked nearly three city blocks in opposite directions.
Colin Johnson, an Obama supporter, said the Illinois senator is not a typical politician. "I'm convinced he's a once-in-a-generation leader," he said.
"He's young and energetic and Washington and the White House could benefit from some fresh air," said Joe Lewis, another Obama supporter.
But Tony Donovan said Obama can use some more seasoning. Donavan was supporting Clinton because she, like him, was a baby boomer who shared similar values and because she has the experience and the team to lead in Washington.
"Obama's a great guy. He'll be great in eight years," Donovan said. "He doesn't have the experience in the Senate. He doesn't have the experience in Washington. He's not ready."
Both campaigns hit Maine heavily with radio and TV advertising, and voters' homes were being called with pre-taped messages in support of both candidates.
On Sunday, Massachusetts Gov. Deval Patrick, Rep. Patrick Kennedy of Rhode Island and Sen. John Kerry of Massachusetts, the 2004 Democratic presidential candidate, were scheduled to visit Maine caucuses on Obama's behalf.
On Clinton's side, Baldacci, Massachusetts Rep. Jim McGovern and New York Rep. Gregory Meeks were to campaign.