Republican Governor Chris Christie on Friday vetoed a bill to make New Jersey the latest US state to legalise gay marriage, but hours later a similar measure advanced by a razor-thin margin in Maryland and appeared destined to become law.
Christie, a rising star in the US Republican Party, accompanied his veto with a call for lawmakers in the state capital Trenton to appoint an advocate for same-sex couples under the state's existing civil union law.
The Democratic-controlled New Jersey legislature does not appear to have the votes to override Christie's veto.
In Maryland's capital Annapolis, the House of Delegates voted 71 to 67 to approve legislation to allow gay marriage, prompting cheers from a packed chamber gallery after two hours of often impassioned debate. The bill heads to the state Senate, which last year approved similar legislation and is widely expected to do so again. Maryland Democratic Governor Martin O'Malley supports gay marriage and would sign the bill into law.
"Today, the House of Delegates voted for dignity," O'Malley posted on Twitter. He later added in another tweet, "Love is an inalienable right."
Seven of the 50 U.S. states have legalized gay marriage - New York, Massachusetts, Connecticut, Vermont, New Hampshire, Iowa and Washington state, as did Washington, D.C. The gay marriage law in Washington state has not yet taken effect.
This week's dramatic battles in New Jersey and Maryland brought an even greater focus to the national debate over same-sex marriage.
Already a contentious social issue, gay marriage has gained more prominence ahead of the Nov 6 US presidential election, with advocates framing it as a civil rights issue and opponents saying marriage should be reserved for unions between a man and a woman.
Christie, a supporter of Republican presidential hopeful Mitt Romney who is often mentioned as a potential vice presidential candidate, has called for voters in New Jersey to decide the issue. No US state has ever approved same-sex marriage in a referendum.
Christie made no secret of his plans to veto the measure and followed through the day after it won full legislative approval.
He asked lawmakers to quit pursuing gay marriage legislation and instead create an ombudsman for civil unions of same-sex couples who would "carry on New Jersey's strong tradition of tolerance and fairness."
"The ombudsman will be charged with increasing awareness of the law regarding civil unions, will provide a clear point of contact for those who have questions or concerns and will be required to report any evidence of the law being violated. In this way, we can ensure equal treatment under the law," Christie said in a statement.
Democrats do not currently appear to have enough votes to override the veto with the necessary two-thirds majority, though they have until the end of 2013 to try. "When we look back in the annals of history, unfortunately, the governor will see that he was on the wrong side of justice," Assembly Speaker Sheila Oliver, a Democrat, said in a statement. "All the couples disappointed by his action today should take solace in the fact that we are not giving up this fight."
In Maryland, O'Malley lobbied aggressively for the bill this week. One of his chief tasks was to sway black lawmakers, many of whom were hesitant to back an issue opposed by much of the state's black clergy.
The debate over legalizing gay marriage shows no sign of abating in other states.
In Washington, Governor Christine Gregoire signed into law on Monday legislation legalising same-sex marriage, 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.
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.
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.