(RNS) Gov. John Baldacci signed legislation on Wednesday (May 6) that makes Maine the fifth U.S. state to allow same-sex marriages, and only the second to approve the unions without the threat of a court order.

Maine now joins Vermont, Massachusetts, Connecticut and Iowa in allowing same-sex marriage. Lawmakers in neighboring New Hampshire have also taken steps toward approving same-sex marriage, but Gov. John Lynch has not said whether he will sign or veto the bill.

“In the past, I opposed gay marriage while supporting the idea of civil unions,” Baldacci said. “I have come to believe that this is a question of fairness and of equal protection under the law, and that a civil union is not equal to civil marriage.”

Baldacci cautioned, however, that Maine voters could try to overturn the law with a ballot measure, similar to a high-stakes referendum that ended same-sex marriage in California last November.

“Just as the Maine Constitution demands that all people are treated equally under the law,” he said, “it also guarantees that the ultimate political power in the state belongs to the people.”

Maine’s decision comes on the heels of an unprecedented tide of support for gay marriage, both in state capitols and among the general public. A recent ABC News/Washington Post poll found supporters of gay marriage outnumbering opponents, 49 to 47 percent, for the first time in that poll’s history.

On Tuesday, Washington D.C.’s City Council voted 12-1 to recognize same-sex marriages performed in other states and countries, setting the stage for a possible showdown in Congress, which has finally say on all D.C. laws.

Tony Perkins, president of the Washington-based Family Research Council, urged Mainers to collect enough signatures to overturn the new law. “Because of the profound importance of man-woman marriage to the nation, we … urge the citizens of Maine to exercise their right to a ‘People’s Veto’ and halt this move toward counterfeit marriage,” he said.

Liberals, meanwhile, welcomed the decision. “State by state, love and fairness are prevailing over fear and ignorance,” said the Rev. William Sinkford, president of the Unitarian Universalist Association. “America is stronger when all of our families can be legally recognized and protected.”