As same-sex marriage supporters celebrate victories in Washington and Maryland this month, they are keeping a wary eye on New Hampshire, where lawmakers may soon vote to repeal the state’s two-year-old law allowing gay couples to wed.

A repeal bill appears to have a good chance of passing in the State House and Senate, which are both controlled by Republicans. The bigger question is whether they can muster enough votes to overcome a promised veto from Gov. John Lynch, a Democrat.

Based on party lines, House and Senate Republicans both have veto-proof majorities. But this is an issue where party allegiance gets muddy.

In a state whose “Live Free or Die” motto figures into many a policy decision, even many opponents of same-sex marriage wish the issue would just disappear. Republican lawmakers with libertarian leanings, a sizable group, seem especially unhappy to be facing a repeal vote, as well as those who maintain that cutting spending should be the legislature’s sole concern. Both groups appear worried about a backlash from their constituents.

Representative Andrew Manuse, a Republican, said in an e-mail that he would support a repeal because he objected to government “using its power to redefine a religious, social and societal institution.” But he added, “I really am not focusing on this issue.”

Should the repeal pass, New Hampshire would be the first state in which a legislature has reversed itself on the issue of same-sex marriage. In Maine, voters repealed a marriage law through a referendum in November 2009, shortly after the Legislature approved it. This fall, a ballot initiative will ask voters to make same-sex marriage legal again. The California Supreme Court ruled in 2008 that same-sex couples there had a right to marry, but voters banned same-sex marriage in an initiative later that year. The issue remains in court.

Alexander Cohn/Concord Monitor, via Associated Press

Protesters advocating repeal of same-sex marriage demonstrated this month in Concord, N.H.

In a recent poll by the University of New Hampshire Survey Center, 59 percent of respondents were either strongly or somewhat opposed to repealing the law, while 32 percent said they supported repeal.

Representative David Bates, a Republican, filed the repeal bill in January 2011, shortly after Republicans took control of the legislature. But House leaders postponed a vote, saying they needed to focus on the budget. Under legislative rules, the bill must come up for a vote this year, although lawmakers could vote to table it again.

A House vote would need to take place by March 29, the deadline for the House to send its legislation to the Senate. Mr. Bates said Monday that he was working on ways to broaden the bill’s support in both chambers, like changing or removing a sentence that states, “Children can only be conceived naturally through copulation by heterosexual couples.”

“I recognize there’s things in it that some aren’t happy with,” he said, “so we’re going to change it, get it to a place where as many people as possible are comfortable with it.”

Mr. Bates dismissed the University of New Hampshire poll findings, saying, “It’s just not credible to suggest the people of New Hampshire are the aberration of the nation.”

A New York Times/CBS News poll conducted this month found that 40 percent of respondents supported same-sex marriage, while 23 percent supported civil unions for gay couples and 31 percent said there should be no legal recognition of a gay couple’s relationship.

When New Hampshire became the sixth state to approve same-sex marriage, in 2009 — following California, Connecticut, Iowa, Massachusetts and Vermont — it was not an easy feat. The law passed with close votes in both chambers, which were then under Democratic control, and with last-minute support from Governor Lynch, who had preferred civil unions.

Since then, about 1,900 same-sex couples have wed in the state. The repeal bill would not invalidate those marriages, but would allow only civil unions for gay couples moving forward.

Same-sex couples can currently marry in Connecticut, Iowa, Massachusetts, New Hampshire, New York, Vermont and the District of Columbia. Lawmakers in Washington State approved a same-sex marriage law this month, and Gov. Martin O’Malley of Maryland is poised to sign one this week, though opponents are seeking referendums to nullify both laws. New Jersey passed a similar bill this month as well, but Gov. Chris Christie, a Republican, vetoed it.

Meanwhile, voters in Minnesota will decide in November and in North Carolina in May whether to enact constitutional bans on same-sex marriage. Such bans already exist in about 30 states.

Mr. Bates said that if the repeal bill failed this year, he would not give up. Governor Lynch is leaving office at year’s end, and both Republicans who have entered the race to succeed him support repeal.

But Representative Seth Cohn, a libertarian Republican who opposes the repeal, said he thought it would in fact harm the Republicans’ chance of staying in power after 2012, whether or not it succeeds.

“They want this as an election issue,” he said of the Democrats. “I think it’s going to backlash against the Republicans who, in the face of the polls, are choosing not to believe the average person is O.K. with this situation.”

This article has been revised to reflect the following correction:

Correction: February 28, 2012

An earlier version of this article misstated the month when voters in North Carolina will decide whether to enact constitutional bans on same-sex marriage. It is in May, not November.

http://www.nytimes.com/2012/02/28/us/gay-marriage-law-in-new-hampshire-may-be-revoked.html?_r=1