That was a surprise because polls at the time indicated that a majority of voters would approve it. And therein lies the hope of the opposition here this year; while state and national polls suggest that a majority supports same-sex marriage, voters have not always told pollsters the truth.

“I’ll be surprised if we don’t win,” said Carroll Conley Jr., executive director of the Christian Civic League of Maine and a board member of Protect Marriage Maine, a group leading the opposition.

“When it’s framed as ‘Should people be able to marry regardless of sexual orientation?’ you see a significant change from five years ago,” he said. “But if you ask, ‘Should marriage be defined as one man, one women?’ we don’t see significant changes.”

The proposed wording of the ballot question here is, “Do you want to allow same-sex couples to marry?” But proponents want it to point out that neither clergy nor religious institutions would have to perform or host a marriage against their beliefs, a clause that could ease some fears. A decision on the wording is due from Maine’s secretary of state by the end of July.

Mr. Conley said he doubted voters would approve same-sex marriage, in part because people resist change. “From a purely political perspective, a ‘no’ is easier than a ‘yes’ on any referendum.” he said.

Some money for the opposition campaign is coming from collection plates passed at churches. But most is expected to come from the National Organization for Marriage, which funneled almost $2 million into Maine to help defeat the measure in 2009.