The Senate's 24-16 vote sends the bill to the Assembly, which is expected to pass it on Thursday.
Monday's vote contrasts with the only other gay-marriage vote taken in the Legislature. In January 2010, gay marriage supporters thought they had built a narrow majority in the Senate, but senators began to defect, and the measure was defeated 20-14. Since then, Senate President Stephen Sweeney, a Democrat from West Deptford, has changed his position. He says he regrets abstaining two years ago and has made gay marriage recognition a top priority.
Six states and Washington, D.C., allow gay marriage, and Washington state will be added to that list when Gov. Christine Gregoire signs legislation legalizing same-sex marriage Monday.
Christie, a Republican, announced his veto intentions last month. He has said he does not believe marriage laws should be changed but does support New Jersey's civil union law, which grants gay couples the legal protections of marriage.
Christie said he wants to put a change in the definition of marriage to a public vote.
But gay rights groups oppose a referendum. They see gay marriage as a civil rights matter and argue that it should not be up to the masses to protect the rights of a minority group. They also believe that a nasty campaign from social conservatives could erode the narrow majority of support that public polls show gay marriage has in New Jersey.
Gay rights groups are looking at two other avenues to make gay marriage reality in New Jersey. If Christie vetoes the measure, the Legislature would have until January 2014 to override it by getting two-thirds of the votes in each chamber. Advocates hope that with nearly two years, they can change enough votes to get the legislation adopted.
The other route is through the courts. Five years ago, New Jersey's state Supreme Court ruled that gay couples should have the same rights as married heterosexual couples. In response, the Legislature created civil unions.
Gay rights advocates say that because the designation is hard to understand and still treats committed gays differently from married couples, the courts should eliminate civil unions and recognize gay marriage. A lawsuit seeking to do that is in the state court system.