"Absolutely. The trajectory is moving forward. It's clear," said Rea Carey of the National Gay and Lesbian Task Force at a four-day annual gathering of around 3,000 lesbian, gay, bisexual and transgender (LGBT) activists in Baltimore.
Setbacks such as Proposition Eight, which saw voters in California in 2008 erase the right of same-sex couples in that state to wed, are only part of the "push and pull of history," Carey told AFP in an interview.
Increasingly, public opinion accepts the notion of gays and lesbians tying the knot in the eyes of the law, while a growing number citizens who remain opposed are conceding it is going to happen anyway, she said.
"We fall in love, we create families -- and we want the same protections that other families have," she said.
The legal status of same-sex marriage and civil unions -- already recognized in seven states, including New York, plus the District of Columbia -- is shaping up into a major issue this election year.
Legislators in Maryland, New Jersey and Washington are considering bills to legalize such marriages, and this week Maine inched closer to putting its own same-sex marriage law, defeated in a 2009 referendum, to a second vote.
Proposals for constitutional bans on same-sex marriages are meanwhile to be put to a vote in North Carolina in May and in Minnesota in November -- prompting Carey later Thursday to urge activists to be engaged on all fronts.
"We will be playing offense and defense," she said in a "state of the LGBT union" address to the annual Creating Change conference in Baltimore that wraps up on Sunday.
At the federal level, activists also want to see the repeal of the Defense of Marriage Act, in effect since 1990, which defines marriage only as a union between a man and a women.
Social conservatives, including evangelicals and the Roman Catholic church, have led the charge against same-sex marriage, and their votes are being aggressively wooed by Republican presidential hopefuls.
"It's at a minimum unfortunate, and at times offensive, what the GOP candidates have said, because none of them is LGBT supportive," Carey, who has been at the helm of the Task Force since 2008, told AFP.
"History will pass them by, and in the long run it is at their peril that some members of the GOP have not only not been supportive, but have actually been very anti-gay, anti-LGBT."
Having the right to marry makes it possible for long-term gay and lesbian couples to tap into the same rights and benefits that heterosexual married couples take for granted, Carey said.
"We know of (LGBT) couples when, if one partner dies, the other is no longer able to live in the house they've lived in for decades" because -- unlike in a heterosexual marriage -- he or she cannot draw on the deceased partner's Social Security benefits, she explained.
Conference participants widely agree that Barack Obama's presidency has been the most gay-friendly in history, but they recognized a pressing need for more like-minded and outspoken supporters on Capitol Hill.
"We need to elect members of Congress who support LGBT issues from the front porch, not the back garden," Adrian Shenker, president of Equality Pennsylvania, an LGBT organizing and policy group, told AFP.
