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 state’s voters will decide today whether to repeal a law that would allow gay marriage. The law was passed by the Legislature and signed by Democratic Gov. John Baldacci last May but has never taken effect.

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.