With 87 percent of the participating precincts reporting, Obama led in state delegates elected over Clinton, 1,837 to 1,277, with 17 uncommitted.
Obama won at least 13 of Maine's delegates to the national convention, with three still left to award. Clinton won at least eight. In the overall race for the nomination, Clinton leads with 1,135, including separately chosen party and elected officials known as superdelegates. Obama has 1,106.
The voting came a day after Obama and Clinton made personal appeals here, and after Obama picked up wins in Louisiana, Nebraska and Washington.
Organizers had expected heavy participation at the caucuses, but snow was falling and gusting winds hit as many of the gatherings were scheduled.
The weather didn't appear to have hurt turnout. Caucuses started late in Bangor and several other locations across the state because so many people showed up that they were lined up outside the doors.
In Maine's largest city, 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 in Portland, 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."
A line waited to get into Augusta's caucus as Gov. John Baldacci, a Clinton supporter, addressed the crowd of a couple hundred at the city's Cony High School. Asked why he decided to wait in line to participate, John Brandt said, "Getting rid of Republicans, once and for all."
Though Maine's national delegate count is small, Clinton and Obama, along with surrogates, came to the state Saturday as their campaigns drew tighter after Super Tuesday.
Thousands of people packed the Bangor Auditorium to hear Obama on Saturday and hundreds more who weren't allowed inside greeted him as he arrived. People also were stopped at the door as Clinton held a town hall-style gathering nearby at the University of Maine at Orono. She later stopped in Lewiston.
Clinton's daughter, Chelsea, and husband, Bill, also visited, while Obama supporter Sen. Edward M. Kennedy of Massachusetts campaigned in two cities in the days before the vote.
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, visited Maine caucuses on Obama's behalf.
On Clinton's side, Baldacci, Massachusetts Rep. Jim McGovern and New York Rep. Gregory Meeks campaigned.
The high level of excitement across the state contrasted with earlier expectations that the post-Super Tuesday timing of the caucuses would dampen voter interest.
A competitive GOP race a week earlier also helped to enliven interest in the Maine Republicans' nonbinding caucuses, which were won by Mitt Romney. He dropped out of the race last week, making it likely that Arizona Sen. John McCain would become the GOP nominee.