After a watershed year for gay marriage in the United States that included ballot victories and a presidential endorsement, advocates have staked out a handful of states where they believe the next round of fights over same-sex unions can be won.

But any victories will not come easily.

Those who defend marriage as a union of one man and one woman plan to use the November 6 defeats as a rallying cry and fundraising tool. The National Organization for Marriage, the leading group opposed to gay marriage, has called on allies to raise $30 million in the coming year - more than double its haul in 2012.

"Frankly, Americans never really thought that they would have to defend something so obvious as the reality that it takes a man and a woman to make a marriage, and only recently has the threat become clear," Brian Brown, the organization's head, said in an interview.

"We're committed to not letting that happen again, to being outspent in that way. And I think a lot of our donors will step up to the plate, in a way that you haven't seen before, in any future state fights."

This Election Days, voters in Maine, Maryland and Washington state approved ballot initiatives legalizing same-sex marriage, marking the first time in U.S. history voters approved gay marriage at the polls, and bringing to nine the number of states allowing gay marriage.

Weeks later, both sides are preparing for more wrenching battles.

In Rhode Island, the last of the New England states where marriage is limited to straight couples, lawmakers are reviving a gay marriage bill that failed last year.

"From a strategic point of view, we feel very well positioned to capitalize on the momentum that's been generated over the past year," said Ray Sullivan, the campaign director for Marriage Equality Rhode Island.

A poll released in October by WPRI-TV in Rhode Island found 56 percent of voters support allowing same-sex marriage, while 36 oppose it and 8 percent are unsure.

In Minnesota, which on November 6 became the first state to reject a constitutional ban on same-sex marriage, advocates say they now hope to build on voter enthusiasm, pushing lawmakers to take up a bill allowing gay marriage.

In Oregon, same-sex marriage advocates hope to put a pro-gay marriage referendum before voters in 2014. At the moment, Oregon is one of more than 30 states that have amended their constitution to limit marriage to unions between a man and a woman.

Advocates in Illinois and Hawaii, both of which currently allow same-sex unions, are also pushing for marriage votes.

And in New Jersey, where a gay marriage bill passed the legislature last year but was vetoed by Republican Governor Chris Christie, lawmakers say they plan to take up the issue again.

Loretta Weinberg, a Democratic New Jersey state senator, said the legislature is "within striking distance" of the needed two-thirds majority. But to give Republican supporters political cover against a conservative backlash, she said, it was unlikely the bill would be introduced before the state's June primary.

'WE ARE THE REBELS'

A decade ago, Americans opposed gay marriage by a margin of 57 to 35 percent, according to the Pew Research Center. But the stigma attached to homosexuality has faded and support for gay rights has surged, especially among young people.

Pew's latest survey, from July, found 48 percent of Americans approving of same-sex marriage and 44 percent opposing it. For two straight years, the Gallup Poll has found a slim majority of Americans believe same-sex couples should have the same right to wed as heterosexuals.

This year, Barack Obama became the first U.S. president to say he believed same-sex couples should be allowed to marry. The move was seen as energizing voters ahead of Obama's re-election against Republican challenger Mitt Romney, rather than as a liability.

"If nothing else, I think this election will prove that being for marriage isn't a liability, and it may actually help," said Matt McTighe, campaign manager for Mainers United for Marriage.

"In 2004, if you took a pro-marriage position, the next morning 20 groups would be out to make sure you're defeated," added McTighe, whose organization led the successful campaign for same-sex marriage in the state.

Still, in many states the gay marriage fight remains an uphill battle. The National Organization for Marriage says its own polling has found well over half of American voters believe marriage should be defined as a union of one man and one woman.

But Brown acknowledges that defenders of so-called traditional marriage now find themselves on the defensive.

"All of the cultural power is being exerted on the side of redefining marriage," Brown said. "Therefore, in colleges, students are constantly hearing about how it's discrimination or bigoted to stand up for traditional marriage."

"We are the rebels now," he said.