With more than 80 per cent of precincts reporting, Sanders led Clinton with 64.3 per cent of the vote compared to her 35.5 per cent.
A victory along those lines would see him take most of the state’s 25 convention delegates at stake.
It was an expected win for Sanders, who enjoys strong backing in the region and hails from nearby Vermont.
“I thank the people of Maine for their strong support,” his campaign said in a statement.
“With another double-digit victory, we have now won by wide margins in states from New England to the Rocky Mountains and from the Midwest to the Great Plains.”
Clinton and Sanders also faced off in a televised debate in Flint, Michigan, just two days before a crucial primary in that delegate-rich northern industrial state.
They tackled the scandal surrounding the lead-contaminated water in the city, with Sanders railing against the “disgrace beyond belief” and both calling for more accountability.
On Saturday, Clinton won in Louisiana, the biggest prize of the night, but Sanders won in Kansas and Nebraska.
If his Maine win is confirmed, that would push his total to eight victories in 19 contests.
Clinton was favored in Louisiana thanks to overwhelming support from African American voters, while Sanders has tended to do best in states with largely white voters.
After Saturday’s contests, Clinton had 1,121 delegates, nearly half the 2,383 needed to win the Democratic nomination.
But speaking at the CNN debate, Sanders sought to stress his campaign was on an upswing.
“Just in the last two days, we have won the caucuses in Maine — we won that tonight with a very large turnout — we won Nebraska, we won Kansas, and Kansas was the biggest turnout in their caucus history,” he said.
“I think we are exciting working class people, young people who are prepared to stand up and demand that we have a government that represents all of us and not just the few.
PTI