(Portland, Maine) Bolstered by out-of-state money and volunteers, both sides jockeyed Monday to boost turnout for a Maine referendum that could give gay-rights activists in the U.S. their first victory at the ballot box on the deeply divisive issue of same-sex marriage.

The contest is considered too close to call, and both campaigns worked vigorously – with rallies, phone calls, e-mails and ads – to be sure their supporters cast votes in the off-year election.

If voters uphold the law, it will be the first time the electorate in any state has endorsed marital rights for same-sex couples, energizing activists nationwide and deflating a long-standing conservative argument that gay marriage lacks popular support.

Conversely, a repeal – in New England, the corner of the country most receptive to same-sex marriage – would be a jolting setback for the gay-rights movement and mark the first time voters overturned a gay-marriage law enacted by a legislature. When Californians voters rejected gay marriage a year ago, it was in response to a court ruling, not legislation.

Elsewhere around the country, Democratic Gov. Jon Corzine is locked in a tight battle for re-election in New Jersey, Republican Bob McDonnell is heavily favored in the race for Virginia governor, a hotly contested special congressional election in upstate New York has exposed a rift in the GOP between moderates and conservatives, and billionaire Michael Bloomberg is expected to coast to victory in his bid for a third term as mayor of New York.

Apart from Maine, five states have legalized same-sex marriage – Iowa, Connecticut, Massachusetts, Vermont and New Hampshire. But all did so via legislation or court rulings, not through a popular vote. By contrast, constitutional amendments banning gay marriage have been approved in all 30 states where they have reached the ballot.

“The eyes of the nation will be on Maine,” said Rea Carey, executive director of the National Gay and Lesbian Task Force. “The stakes are high, but so is our hope that Maine will remain among the growing number of states that extend the essential security and legal protections of marriage to all loving, committed couples.”

Brian Brown of the New Jersey-based National Organization of Marriage, which has contributed $1.5 million to the repeal campaign, agreed the election is critical for both sides.

He took heart in polls showing a close race, saying polling in other states that voted on the issue tended to underestimate the eventual opposition to same-sex marriage.

“New England is the one area where it’s much tougher ground for us than other states,” Brown said. “The fact that in a state like Maine we’re polling relatively even shows the depth of support for saying marriage is between a man and a woman.”

In downtown Portland, hundreds of people carrying signs gathered for a raucous noontime rally Monday in favor of gay marriage. Participants were exhorted to go to City Hall to vote – and make sure others vote as well.

Meredith Hunt, who hopes to wed her partner of 15 years, Melissa Hamkins, has been doing door to door, working the phones and recruiting volunteers. She took time off from her job as a nurse practitioner Monday to join in the final push for gay marriage.

“I’m running on adrenaline at this point. I don’t want to leave any stone unturned,” said Hunt, 45, who lives on a farm in Bowdoin. “This isn’t politics. This is personal.”

On the other side, Jeannette Saucier, 71, of Topsham, telephoned potential voters in hopes of stopping gay marriage.

“It’s not that I feel bigoted to gay people. We have gay people in my own family, but I don’t see them having to be married to prove a point,” she said.

Both campaigns have attracted volunteers and hefty financial support from out of state, but the financial advantage went to the side defending same-sex marriage, Protect Maine Equality. It raised $4 million, compared with $2.5 million collected by Stand for Marriage Maine, which forced the repeal vote through a petition drive.

Marc Mutty, on leave from a job with the Roman Catholic Diocese of Portland to run the Stand for Marriage campaign, said in a homestretch appeal for donations that the election “is about the future of marriage in Maine, and thus the nation.”

“It is about whether marriage will continue to be between one man and one woman as God intended and human history has affirmed, or if we will plunge our state into a radical social experiment of ‘any two will do,’” he said.

The diocese coordinated $550,000 in contributions to the repeal campaign and has criticized Baldacci, a Catholic and former altar boy, for signing the marriage law.

Gay-marriage opponents have stressed the theme – disputed by their rivals – that gay marriage will be taught in schools if the law is allowed to stand. A Stand For Marriage radio ad Monday focused on an attempt to strip the state license from a high school counselor who spoke out against gay marriage in a television commercial.

“Don’t be fooled. If Question 1 fails and homosexual marriage is legalized, those in power in Maine schools will push it on students just as they are trying to punish one of Maine’s best educators for supporting traditional marriage,” the radio ad said.

Gay rights was also on the ballot Tuesday in Washington state, where voters will decide whether to uphold or overturn a recently expanded domestic partnership law that gives same-sex couples the same state-granted rights as heterosexual married couples.