(CNN) -- Proponents of same-sex marriage got a boost on two fronts Monday, when the governor of Washington signed a bill legalizing marriage for gay and lesbian couples and the New Jersey state Senate voted 24-16 in favor of a similar bill.
The New Jersey bill now goes to the Assembly, which is slated to vote Thursday. "We're cautiously optimistic" about its chances for passage, said Steven Goldstein, a spokesman for Garden State Equality, which has lobbied for the bill.
But the legislation is threatened in both states.
New Jersey Gov. Chris Christie said last month that the issue "should not be decided by 121 people in the State House in Trenton." Instead, he favors a statewide referendum.
"I think that this is not an issue that should rest solely in my hands, in the hands of the Senate president or in the hands of the speaker or the other 118 members of the Legislature," he said. "Let's let the people of New Jersey decide what is right for the state."
If he vetoes the measure, "the battle for overriding the veto begins," Goldstein said.
Gov. Chris Gregoire's signature to legislation legalizing same-sex marriage added her state to a list that includes Massachusetts, Vermont, New Hampshire, Connecticut, Iowa, New York and the District of Columbia.
The law will go into effect in June, when the legislative session ends, but opponents have vowed to try to halt its implementation by putting it on the November ballot.
That possibility did not appear to dampen the spirits of those who attended the bill-signing ceremony.
"We have finally said yes to marriage equality," Gregoire said to applause moments before signing the bill. "It gives same-sex couples the same right to a marriage license as heterosexual couples."
She noted that churches are not required to perform same-sex marriages under the law and expressed confidence that, if put to a state-wide vote, Washingtonians would back the measure.
"I believe our Washingtonians will say yes because it's time for us to stand up for our sons and daughters, our brothers and sisters, our moms and dads, our friends and the couple down the road," she said. "It is time to give our loving gay and lesbian couples the right to a marriage license in Washington state."
But the news for same-sex marriage advocates is not all positive. In states where legislators have passed Defense of Marriage Acts, which define marriage as being between a man and a woman only, they are taking defensive action. North Carolina is set to vote in a May primary election on such an act, and Minnesota is to hold such a vote in November.
In 2009, Maine legislators passed a same-sex marriage bill that drew challenges by opponents who pushed for a referendum that ultimately overturned the law with 53% of the vote. Proponents are trying to get it back on the ballot this year. Gay rights advocates have garnered thousands of signatures in an effort to force a second referendum in November.
In California, a 2008 public vote outlawed gay and lesbian couples' right to wed.
Two years later, a federal district court overturned the voter-approved measure known as Proposition 8, saying couples were unfairly denied their rights. A federal appeals court ruled last week against California's ban, arguing that it unconstitutionally singles out gays and lesbians for discrimination.
The ban has remained in place during the appeals process and could soon get a ruling from the U.S. Supreme Court.
Similar battles have unfolded in Maryland, where same-sex marriage opponents have pressed for referenda to counter bills that appear to enjoy growing support in their statehouse.
The National Organization for Marriage, which opposes same-sex marriage, predicted that the referenda will block the marriages from taking place.
"Ultimately, the people are going to decide, and we're confident that the people will vote to protect marriage as the union between a man and a woman," President Brian Brown said. "The legislature's decision is a decision against the will of the people."
Marriage, he said, is by definition the union of a man and a woman. "The state did not create that definition; the state merely recognizes it."
Statewide votes are not the way to handle the issue, according to Thalia Zepatos, director of public engagement for Freedom to Marry. "The question I like to pose to people is: Would you like the entire state to vote on whether you could marry your husband or wife?" she asked.
But the trend among Americans seems to be moving toward acceptance of the practice. A CNN/ORC International Poll carried out in September found that 53% of respondents said marriages between gay or lesbian couples should be recognized as valid, up from 44% in 2009. The poll had a sampling error of plus or minus 3 percentage points.
In September's poll, Democrats favored recognizing them as valid by 67% to 31%, independents by 53% to 46%. Just 30% of Republicans said they favored recognizing same-sex marriage as valid, versus 69% who did not. Those results had a sampling error of plus or minus 6 points.