As secretary of state, Hillary Clinton addressed the rights of lesbian, gay, bisexual and transgender people from around the world in her "Free and Equal in Dignity and Rights" speech on International Human Rights Day at U.N. premises in Geneva Dec. 6, 2011. She is now running for president as a pro-LGBT rights candidate. Reuters

Hassan Naveed has closely followed politics for years, but as a gay man he grew used to seeing his life and beliefs not mirrored back to him in glossy campaign advertisements or the sweeping rhetoric of a candidate's stump speech. He expected more of the same Sunday when he went to Hillary Clinton's new presidential website to watch her campaign announcement video. Within minutes, a handsome gay couple filled his screen, casually discussing their wedding plans in an everyday tone that belied the historic significance of the moment. For the first time, a major presidential candidate had featured a gay couple in a campaign announcement video.

"I was surprised, happy, elated," said Naveed, a 28-year-old graduate student in New York City. "As soon as I saw that I was like, 'Wow, this is awesome!' The last presidential election, this wasn’t necessarily part of the campaign narrative, and being able to see something like this from the onset, it was surprising."

Clinton's grand campaign unveiling and its unprecedented embrace of the LGBT community signaled her latest evolution on gay marriage nearly two decades after her husband, former President Bill Clinton, signed into the law the Defense of Marriage Act. The announcement video and her hiring of an openly gay campaign manager, another first for a White House contender, suggest Clinton is poised to make gay rights a centerpiece of her campaign at a time when marriage equality laws are increasingly mainstream but still not universal across the nation.

Gay rights activists and LGBT leaders said Clinton's groundbreaking campaign illustrates more voters -- not just LGBT people and their advocates -- want candidates who support gay marriage. At the same time, while LGBT organizations were eager to praise Clinton's message, they said her former support for the federal law that defines marriage as the union of a man and woman remains troubling and raises questions about whether Clinton will be a leader or follower in the growing gay rights movement if she is elected president.

"She is clearly making a play for the LGBT community and that’s smart not just for that vote, which is a sliver for the community, but also because in recent years we have gained allies among our moms and dads and friends, and I get the sense that they are judging candidates by where they stand on LGBT issues," said Denis Dison, senior vice president of the Gay & Lesbian Victory Fund, which recruits LGBT candidates for political office.

Clinton can expect challenging questions on the campaign trail from the LGBT community, such as whether she supports transgender people serving in the military, and what position the Supreme Court should take on state gay marriage bans, Dison said. "She will still have to win over voters," he said.

Brian Silva, executive director of Marriage Equality USA, said Clinton was part of a growing movement of politicians on both sides of the political aisle who have come out for gay rights in recent years as more Americans demand marriage equality. He said the symbolism of Clinton's campaign message was significant.

"Whenever we see our faces, our lives and our families reflected in political positions and businesses and in any kind of institution like that, it reflects where we’ve come, it reminds us that we still have a ways to go and it also inspires a new generation of young people that are questioning or struggling with coming out that they have places to go, that there is a future for them, that they can have whatever job they want and be the person they want to be," he said.

Clinton's historic campaign announcement stands out further compared to her Republican rivals' positions on LGBT issues, namely their support for Indiana's recent religious freedom law that critics have decried as anti-gay because it would allow small business owners to refuse service to gay weddings for religious reasons. U.S. Sens. Ted Cruz, Rand Paul and Marco Rubio, who are all running for president, as well as former Florida Gov. Jeb Bush, who is weighing a presidential bid, all endorsed Indiana's Religious Freedom Restoration Act in recent weeks. Clinton came out against the law. "Sad this new Indiana law can happen in America today," Clinton tweeted in early April. "We shouldn't discriminate against ppl bc [sic] of who they love."

JoDee Winterhof, vice president of policy and political affairs for the Human Rights Campaign, an influential LGBT advocacy group, said it was exciting to have "a pro-equality candidate" running for president. "The unfortunate reality is that many of the current field of Republican candidates have opposed nondiscrimination legislation and marriage equality," Winterhof said in a statement Monday.

Nationwide, 52 percent of Americans now support gay marriage, according to the Pew Research Center. A strong majority of LGBT people back allowing gays and lesbians to marry legally, with 78 percent of those who identify as Republican saying they “strongly favor” or “favor” same-sex marriage compared with 96 percent who said the same and voted Democrat.

Clinton defended DOMA as recently as 2000 when she said as a U.S. Senate candidate in New York she would have signed the law. More than a decade later, she cemented her status as a beloved gay icon with a forceful speech before the United Nations in Geneva while secretary of state in which she said: "Being LGBT does not make you less human. And that is why gay rights are human rights, and human rights are gay rights."

"That statement went a long way toward cementing her reputation as a champion for the LGBT community," Dison said. "That is about as declarative a statement you can make on the world stage and really put the power of the United States behind an issue that in previous administrations was not discussed, or in some cases, the U.S. was on the wrong side of to secure equality for LGBT people."

More recently, records released by the National Archives at the Clinton Library showed Hillary Clinton’s staff defended gay-rights issues and quietly battled anti-gay-rights legislation during Bill Clinton's presidency, Politico reported.

A Hillary Clinton White House would be a bolder LGBT ally, her campaign seems determined to assure supporters. Clinton's new campaign manager, Robby Mook, ran Terry McAuliffe's successful 2013 campaign for governor of Virginia. He is openly gay.

Meanwhile, engaged couple Jared Milrad, 31, and Nathan Johnson, 30, appeared only briefly among other American families in the video Clinton used to announce her candidacy for president Sunday. Milrad, a lawyer and nonprofit founder, and Johnson, a health care consultant, had no idea the video would be used as part of her campaign announcement. “I think there’s a feeling of a responsibility we both have … that we are the face of the gay community in the video," Milrad told ABC News. "We just want to do that justice and be a voice as much as possible for the LGBT community.”

LGBT people are, in fact, taking note. Naveed, who voted for President Barack Obama in 2008 after wrestling with potentially supporting Clinton instead, said he would never vote for a candidate who didn't side with marriage equality. He said he was impressed by Clinton's experience and was eager for the nation to have a woman president. But he noted her endorsement of LGBT rights mattered "1,000 percent."

"This is a personal cause," he said.