CAMDEN, New Jersey (AP) – After being rebuffed in the U.S. Senate, some opponents of same-sex marriage think losing a court case might help their cause of banning same-sex unions across the country.

High courts in New Jersey, New York and Washington state are deliberating cases in which same-sex couples argue their state constitutions give them the right to marry. Similar lawsuits are working their way through the court systems in California, Connecticut, Iowa and Maryland.

“If any of those courts mandate genderless marriage, you’re going to have folks on the other side saying, ‘This makes the marriage issue serious business,’” said Monte Stewart, president of the Marriage Law Foundation, an Orem, Utah-based group that opposes same-sex marriage.

Since 1999, three state high courts – in Massachusetts, Hawaii and Vermont – have ruled that their states should treat same-sex couples the same as heterosexual couples.

Each ruling was followed by either a backlash or a compromise.

In Hawaii, the state constitution was quickly amended to allow lawmakers to ban same-sex marriage, which they did.

In Vermont, lawmakers created civil unions, which give same-sex couples nearly all the rights of married couples.

Massachusetts is the only state where there are state-recognized same-sex marriages. But ever since the state Supreme Judicial Court said in 2003 that they must be recognized, there has been a major push for a state constitutional amendment to ban them.

The Massachusetts ruling was also seen as a major factor that galvanized opponents of same-sex marriage in the 11 states that passed constitutional bans on it in 2004.

If more judges rule the way the Massachusetts court did, there could be a wider backlash against judges defining marriage, say some conservative activists.

“You lose a battle here, you lose a battle there,” said Len Deo, president of the New Jersey Family Policy Council. “It helps to educate the public and motivate the constituency.”

And that, he said, might pressure Congress to move ahead with a federal amendment banning same-sex marriage. While 19 state constitutions have been so amended, federal lawmakers in Washington, D.C., have been reluctant to amend the U.S. Constitution. On June 7, the U.S. Senate voted 49-48 in favor of an amendment – 18 votes short of enough to pass.

The Marriage Law Foundation’s Stewart said seeing a second state allow same-sex unions would be more significant than Massachusetts – and a bigger unifying force for conservatives.

That is because other states do not have laws like one in Massachusetts that effectively prevents out-of-state same-sex couples from being married there. It is expected that if another state allowed same-sex marriages, same-sex couples would flock there to exchange vows and then return to their home states to mount legal challenges to try to have their marriages recognized.

Gay rights leaders say they are prepared for strong efforts to undo any gains they make in state courts.

In New Jersey, Steven Goldstein of the gay rights organization Garden State Equality said if the state’s high court allows same-sex marriage, he is prepared for a political fight over a state constitutional amendment seeking to trump the ruling.

National gay rights groups also are bracing for backlashes that may come if they succeed in state courts.

“We have to fight to hold the victories we secure,” said Kate Kendell, director of the San Francisco-based National Center for Lesbian Rights. “That is the history of every civil rights struggle.”

Though it may galvanize opponents if any additional states allow same-sex marriage, Bruce Hausknecht, judicial analyst for Focus on the Family Action, a conservative lobbying group based in Colorado Springs, Colo., said he does not want to see any states allow same-sex unions.

But Hausknecht also said the courts he worries most about are not the state courts, but federal courts such as those in Nebraska and Georgia that have struck down those states’ anti-same-sex marriage amendments.

“The impact of federal decisions go beyond just the state where the federal court sits. We’re definitely gravely concerned about federal judges redefining marriage,” he said.