By KATE ZERNIKE
TRENTON — The New Jersey State Senate voted on Monday to legalize same-sex marriage, a significant shift in support from two years ago, when a similar measure failed.
The legislation faces a vote on Thursday in the State Assembly, but even if that chamber passes the measure, as expected, Gov. Chris Christie, who favors holding a referendum on the issue, has said he will veto it.
But advocates hailed the Senate vote as a huge advance, noting that they won 10 more votes than they did two years ago. And both supporters and opponents said they were surprised by the margin: the bill needed 21 votes to succeed and passed 24 to 16.
“The margin brought the notion of an override out of fantasyland,” said Steven Goldstein, chairman of Garden State Equality, a gay rights group. “Before today, I would have said the chances of an override were one in a million. Now I’d say it’s about one in two.”
Overriding the anticipated veto would require the approval of two-thirds of both houses, which in the Senate translates to 27 votes. But Democrats, who control the Legislature and have made the bill their top priority this year, argue that they have nearly two years — until the session ends on Jan. 14, 2014 — to muster just three more votes than they won on Monday.
Most significantly, supporters won the support of the Senate president, Stephen M. Sweeney, who abstained from voting two years ago. He has since called that the biggest mistake of his political life, and is the bill’s chief proponent. As the tally was flashed on a board above the Senate chamber, Senator Sweeney, a Democrat from Gloucester County, thrust a thumbs-up in the air.
“These are human beings with feelings that love their partners and they want to be married,” he said. “So be it.”
It was the first time a chamber of the Legislature endorsed the idea of same-sex marriage.
Just one senator, Gerald Cardinale, a Republican of Bergen County, spoke against the measure, arguing that it cheapened the institution of marriage. “This bill simply panders to well-financed pressure groups and is not in the public interest,” he said.
Senator Jennifer Beck, of Monmouth County, who voted no two years ago, was one of two Republicans to vote yes this time. “Our republic was established to guarantee liberty to all people,” she said. “It is our role as elected representatives to protect all of the people that live in our state.”
Seven states and Washington, D.C., allow same-sex marriage, but it has encountered unexpected hurdles in some relatively liberal East Coast states like New Jersey. More than two years ago, Gov. Jon S. Corzine, whom Mr. Christie had recently defeated, promised to sign a bill allowing same-sex marriage in the last days of his administration. But Mr. Corzine’s fellow Democrats could not marshal the votes to get it through the Legislature.
Mr. Christie, a Republican, has said the issue should be put on the ballot in November as a constitutional amendment. Some polls have found that a slight majority of New Jersey voters support same-sex marriage. Advocates note, however, that in 31 states where same-sex marriage has been put to a referendum, it has failed.
On Monday, Mr. Sweeney said there was “not a chance in hell” that he would support the legislation required to put the question to a ballot, which he said would mean allowing “millions of dollars to come into this state to override a civil right.”
Some opponents dismissed the vote, saying the governor’s veto would make it irrelevant.
But Rabbi Noson Leiter, a spokesman for Garden State Parents for Moral Values, which opposes the measure, said he was surprised at how many legislators supported the bill — eight who voted no or did not vote two years ago supported it this time. “If they put it to a referendum, the numbers would be reversed,” Rabbi Leiter said.
In 2006, the New Jersey Supreme Court ruled that same-sex couples were entitled to the same protections as heterosexual couples, but left it up to the Legislature to determine how to guarantee those rights. The Legislature responded with a law allowing civil unions.
Advocates of legalizing same-sex marriage say that the law has created, at best, a system of separate but equal treatment. Seven gay or lesbian couples have sued the state, arguing that civil unions still leave them at a disadvantage in decisions on health care, in retirement benefits and in access to the emotional satisfaction of a legal marriage.
This article has been revised to reflect the following correction:
Correction: February 13, 2012
Because of an editing error, an earlier version of this article incorrectly characterized State Senator Jennifer Beck’s vote. She was one of two Republicans to vote Monday for the bill on same-sex marriage; she was not one of only two senators to vote for it.