New Jersey is the best chance for proponents to add a sixth state allowing same-sex unions. Proponents want the bill passed quickly because Democratic Gov. Jon Corzine has said he'd sign it before leaving office. Republican Gov.-elect Chris Christie, who takes office Jan. 19, has said he'd veto it.
A similar measure was voted down last week in the New York state Senate. Last month, voters in Maine overturned a law that was enacted this year to allow same-sex marriages but never took effect.
Gay marriage is recognized in Massachusetts, Vermont, Connecticut and Iowa. It becomes legal in New Hampshire on Jan. 1.
In 2009, the gay-marriage debate shifted into a new forum: state Legislatures. Before Vermont, New Hampshire and Maine lawmakers voted this year to allow the unions, the rights had been granted only by state courts.
The City Council in Washington, D.C., is expected to vote this month to allow gay marriage there, too.
Public opinion polls show the majority of Americans oppose allowing gays to marry. And that's been reflected in votes on constitutional amendments to ban them. Such amendments have been adopted by voters in 30 states - every one where it's been brought to a vote.
New Jersey is considered a place in the vanguard of gay rights. This decade, it became one of the first states to recognize domestic partnerships, which allowed gay couples some benefits, and civil unions, which give all the legal benefits of marriage to gay couples.
But advocates say the civil unions don't work because they create a "separate but equal" distinction and because most people don't understand them.
Opponents, including many conservative religious organizations, say that allowing gay couples to be married would change the definition of marriage. They also say they fear being forced to recognize an institution that they say runs against their religious beliefs.
The bill before the Senate committee was amended Monday to build in stronger protections for religious organizations so they don't have to perform gay marriages.