A poll released Wednesday shows that 55 percent of Mainers plan to vote in support of same-sex marriage on Nov. 6, and another 1.3 percent are leaning in favor of voting for it, according to Pan Atlantic SMS Group of Portland.

The survey of 400 people, conducted Sept. 24-28, indicates that 39 percent are opposed to the ballot measure to legalize same-sex marriage in Maine and 4.5 percent are undecided. The poll has a margin of error of 4.9 percentage points.

In notes that accompany the poll, Patrick Murphy of Pan Atlantic SMS Group notes that support for gay marriage might be “inflated” because of the way respondents answered more general questions about their level of support for same-sex marriage.

“This suggests a much closer race on this issue than straight up polling by several polling firms indicates,” he wrote.

The numbers are similar to those from a poll by Critical Insights, another Portland firm, which showed 57 percent support legalizing same-sex marriage, 36 percent oppose it and 7 percent are undecided.

That poll was commissioned by the Portland Press Herald/Maine Sunday Telegram.

Two other polls released in September showed 52 percent and 53 percent in support.

Mainers will vote Nov. 6 on Question 1, which asks if they want to allow the state to issue marriage licenses to same-sex couples.

In 2009, Mainers rejected gay marriage 53 percent to 47 percent. A week before that vote, Murphy’s firm released a poll that showed 53 percent in support, 42 percent opposed and 6 percent undecided.