The Assembly vote of 42-33 affirmed a Senate vote from Monday and increased the scrutiny on Christie, a supporter of Republican presidential hopeful Mitt Romney.  

Christie has tried to deflect controversy by saying the matter should be settled by voters in a referendum. No US state has ever approved same sex marriage in a referendum.  

“I realise that for many in this chamber this is not an easy vote,” said Assembly Deputy Speaker John Wisniewski, a Democrat.

“The fight for civil rights has never been an easy fight.”  

Both chambers appear to lack the two-thirds majority needed to override a veto. Christie’s spokesman said the governor would have no comment on the legislation on Thursday, but he has been emphatic in the past about his intention to veto it.  

Later on Thursday, the Maryland House of Delegates began debating a similar initiative legalizing same-sex marriage, highlighting a contentious social issue gaining prominence in a presidential election year.   

The action in the Maryland and New Jersey statehouses follows passage of legislation in Washington state. Governor Christine Gregoire signed the Washington bill on Monday, but it will not take effect until at least June. Opponents are working to gather signatures for a ballot initiative in November that would block the legislation.  

Same-sex couples can marry legally in New York, Massachusetts, Connecticut, New Hampshire, Vermont, and Iowa, as well as the District of Columbia.  

In California, a federal appeals court earlier this month overturned that state’s gay marriage ban, enacted through a 2008 ballot initiative. That sets up a possible showdown in the US Supreme Court over the matter.  

New Jersey’s Democratic leadership, which controls both houses of the legislature, has made gay marriage a top priority this session, saying the state’s civil union law does not adequately protect same-sex couples.  

Republican Jay Webber argued the state’s civil union law grants “all the rights” to gay and lesbian couples.  

“There is no evidence of wholesale trampling of civil rights,” he said.  

Next veto?

The initiative now shifts to Christie, who has 45 days to veto the bill but has vowed to do so immediately.  

Democrats do not appear to have enough votes to override a veto with a two-thirds majority, though they have until the end of 2013 to try.  

The Senate would need 27 votes, or three more than voted in favour of the bill on Monday, to override a veto. The Assembly would need to find an additional 12 votes to reach the required 54.  

Christie called Monday’s Senate vote a “good bunch of theatre” and told reporters, “Well, they won’t get enough votes to override my veto.”  

Christie has said he would prefer to see the state’s voters resolve the issue, a sentiment that was echoed on Thursday at a rally outside the Statehouse, where several hundred people carried signs saying, “Let the people decide.”     

In Maryland, further debate was postponed until Friday in the House of Delegates amid uncertainty whether proponents of the “Civil Marriage Protection Act” had the 71 votes needed to advance it to the state Senate.  

The House adjourned for the day after adopting a single amendment on Thursday to delay the effective date of the bill to January 2013 from October 2012. The extension of the debate over amendments into Friday means that a final vote in the House will probably not happen until next week.  

Comparable legislation passed the Maryland Senate last year but failed in the House when a number of African-American Democrats joined Republicans in opposing the bill.   

Democratic Governor Martin O’Malley, a gay marriage supporter, has attempted to sway the black lawmakers, many of whom are hesitant to back an issue opposed by much of the state’s black clergy.  

The Capitol in Annapolis was the scene of fervent lobbying by dozens of clergy members and others on Thursday.  

Delegate Talmadge Branch, a black Democrat from Baltimore, said the vote was “very close.”  

“I am opposing it based on my district that I represent,” Branch said, describing his district as working class. “It’s basically more geography for me than anything.”  

US federal law defines marriage as between one man and one woman but the administration of President Barack Obama has chosen not to defend the law in court.