U.S. Republican presidential hopeful Mitt Romney won a non-binding nominating contest in the northeastern state of Maine Saturday with 39 per cent of the vote.

Second-place finisher in the Maine caucuses with 36 per cent was libertarian Texas congressman Ron Paul, who campaigned hard in the state even though no delegates were at stake.

Former senator Rick Santorum received 18 per cent of the vote, and former House speaker Newt Gingrich came in last with eight per cent, Maine Republican party chairman Charlie Webster said.

Though Maine is considered merely a beauty contest, Romney's win there was important to reaffirming his frontrunner status after a three-state loss last week to Santorum that raised fresh doubts about the former Massachusetts governor's appeal.

Romney had not spent much time in Maine, but made an 11th-hour visit Friday to rally support. He beat Paul by 196 votes out of the 5,000 cast.