Maine residents will decide today whether to let stand a law permitting same-sex marriage, an effort that has failed in every state where it has been put before voters.

Public opinion surveys in Maine show a dead heat on Question 1, which would cancel the marriage statute that passed the legislature in May and was signed by Gov. John Baldacci, a Democrat.

In the five other states where gay men and lesbians are allowed to marry, the laws were put in place by court rulings or legislatures. None has survived a referendum, but Mr. Baldacci expressed guarded optimism Sunday about the effort in Maine.

"I believe it's something in the water or the air in this state that recognizes individual rights and anti-discrimination attitudes," the governor said by phone from Augusta, the capital. "It's more of a libertarian-type state than it is Republican or Democrat. We have two Republican senators, two Democratic representatives and there have been two independent governors."

The campaign against same-sex marriage in Maine draws heavily from the effort that a year ago overturned a California Supreme Court ruling allowing same-sex marriage. TV commercials produced by Schubert Flint Public Affairs, a Sacramento consulting firm, feature parents lamenting that their young children are being taught in school that marriage between two women or two men is normal.

Nearly identical ads were highly effective in California.

Advocates of same-sex marriage responded to the ads with an opinion from state Attorney General Janet Mills stating that the law would have no effect on what is taught in schools.

"Allowing same-sex marriage does not require teaching of gay marriage in the schools any more than allowing divorce requires teaching of divorce in the schools, or allowing adoption requires teaching of adoption in schools," Ms. Mills said.

Mr. Fish called the opinion irrelevant, because curriculum is largely decided by local school boards. "Neither does it say it won't be taught," he said.

Washington correspondent Daniel Malloy writes the "Pittsburgh On The Potomac" blog exclusively at PG+, a members-only web site of the Pittsburgh Post-Gazette. Our introduction to PG+ gives you all the details.