WASHINGTON -- In a nod to a dramatic shift in public opinion, Barack Obama on Wednesday became the first sitting president to announce his support for same-sex marriage.

In a sit-down interview with ABC's Robin Roberts, Obama completed what has been a markedly long and oft-mocked evolution on the matter.

"I've always been adamant that gay and lesbian Americans should be treated fairly and equally," Obama told Roberts, in an interview that will air in full on ABC's "Good Morning America" Thursday.

(Watch ABC's entire clip below)

"I have to tell you that over the course of several years as I have talked to friends and family and neighbors when I think about members of my own staff who are in incredibly committed monogamous relationships, same-sex relationships, who are raising kids together, when I think about those soldiers or airmen or Marines or sailors who are out there fighting on my behalf and yet feel constrained, even now that Don't Ask Don't Tell is gone, because they are not able to commit themselves in a marriage, at a certain point I’ve just concluded that for me personally it is important for me to go ahead and affirm that I think same sex couples should be able to get married," he said.

The statement constitutes an act of political bravery on the president's behalf, as well as a major victory for the gay rights community, which has been pushing him to declare his support for marriage equality for several years. With the issue back in the news this week, the pressure intensified.

On Sunday, Vice President Joseph Biden told NBC's "Meet The Press" that he was personally comfortable with same-sex marriage, which was followed the next day by Education Secretary Arne Duncan saying the same.

The White House insisted that there was no daylight between the vice president's position and the president's, noting that Biden clarified his statement as being in reference to civil rights for gay couples. But the explanation was largely dismissed by both supporters and critics as a convenient way for the president to signal support for marriage equality without having to declare it himself.

On Tuesday evening, the state of North Carolina passed an amendment that defined marriage as a union between a man and a woman. The president expressed his disappointment with the measure, but it remained difficult to square his opposition to a measure outlawing same-sex marriage with his opposition to same-sex marriage itself.

As the political pressure continued to mount, the president finally chose to speak out Wednesday, with the White House hastily scheduling a sit-down interview.

“It’s interesting, some of this is also generational,” the president said. “You know when I go to college campuses, sometimes I talk to college Republicans who think that I have terrible policies on the economy, on foreign policy, but are very clear that when it comes to same sex equality or, you know, believe in equality. They are much more comfortable with it. You know, Malia and Sasha, they have friends whose parents are same-sex couples. There have been times where Michelle and I have been sitting around the dinner table and we’re talking about their friends and their parents and Malia and Sasha, it wouldn’t dawn on them that somehow their friends’ parents would be treated differently. It doesn’t make sense to them and frankly, that’s the kind of thing that prompts a change in perspective.”

The president's support of same-sex marriage will have little political impact, from a practical standpoint, as much of the activity on the issue is currently occurring in the states and the courts. Already the Obama administration's Department of Justice has stopped defending the constitutionality of the Defense of Marriage Act (DOMA), which defines marriage as a legal union between a man and a woman. Legislation to overturn DOMA outright would likely be blocked by congressional Republicans.

The more promising path for same-sex marriage advocates remains a friendly hearing by the United States Supreme Court.

Still, the symbolism of Obama's remarks is hard to ignore. In becoming the first president to publicly support marriage equality, he sets the bar for its political acceptance. He also has the ability to shape public opinion further on the matter.

Of course, there may be drawbacks to such a strong expression of support. While recent polls show that popular support for marriage equality is gaining widespread acceptance, some pivotal swing states remain largely opposed to the concept. And one of them, North Carolina, remains a major target for the president's reelection campaign.

"The question is, is there a risk?" a prominent Democratic Party official who requested anonymity told The Huffington Post after Biden's remarks. "It is not nationwide [polling] we are talking about. We are talking about Virginia, North Carolina and other swing states. And we are talking about, would Karl Rove and his team stoop to using horribly grotesque and hateful tactics ... and would that peel off 10,000 votes?"

Until Wednesday, that question was hypothetical. Now, it's a critical component of the 2012 election.

Below, reactions to Obama's announcement from around the political world:

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  • Mitt Romney

    "I believe marriage is a relationship between a man and a woman," Mitt Romney said.

  • Kyrsten Sinema

  • Daniel O'Donnell

  • Kirsten Gillibrand

  • Jeff Merkley

  • Elizabeth Warren

  • Michael Bloomberg

    "This is a major turning point in the history of American civil rights," said New York City mayor Michael Bloomberg. "No American president has ever supported a major expansion of civil rights that has not ultimately been adopted by the American people - and I have no doubt that this will be no exception. The march of freedom that has sustained our country since the Revolution of 1776 continues, and no matter what setbacks may occur in a given state, freedom will triumph over fear and equality will prevail over exclusion. Today's announcement is a testament to the President's convictions, and it builds on the courageous stands that so many Americans have taken over the years on behalf of equal rights for gay and lesbian Americans, stretching back to the Stonewall Inn in Greenwich Village."

  • Jerrold Nadler

    "I applaud President Obama for announcing his support for marriage equality today," said Rep. Jerrold Nadler (D-N.Y.) "For the first time in this nation's history, a sitting president has shown the courage and leadership to stand up for all American families by pledging to support the fundamental right of every person to marry the person they love, and to have that marriage fully respected. I commend President Obama for this brave and honest step. Those who seek to politicize civil rights for personal or political gain will certainly attack him, but the course toward marriage equality and justice is the correct and inevitable path."

  • Brad Lander

  • Fred Karger

    "I'm thrilled!" longshot GOP presidential candidate Fred Karger told HuffPost, referring to Obama's embrace of marriage equality. Karger is the first openly gay Republican or Democrat to run for president. "The Karger pressure has worked," he joked. "Particularly after the defeat in North Carolina, we welcome him to the full equality position."

  • Vince Gray

  • Martin O'Malley

  • Sen. Jeanne Shaheen

  • Barack Obama

  • Mark Udall

  • Senator Chris Coons

  • Rep.George Miller

  • Jim Himes

  • Nancy Pelosi

  • Nita Lowey

    "I have been blessed to have a long and happy marriage. I strongly believe all Americans deserve that same opportunity," said Rep. Nita Lowey (D-N.Y.)

  • Antonio Villaraigosa

  • Jackie Speier

  • Michael Steele

  • Dennis Kucinich

  • John Brunner

  • Cory Booker

  • Chris Gregoire

  • Fred Karger

  • Ted Strickland

  • Jared Polis

  • Reince Priebus

    "While President Obama has played politics on this issue, the Republican Party and our presumptive nominee Mitt Romney have been clear. We support maintaining marriage between one man and one woman and would oppose any attempts to change that," said RNC Chairman Reince Priebus.

  • Debbie Wasserman Schultz

  • Chellie Pingree

  • Christine C. Quinn

  • Mike Huckabee

    "Barack Obama just announced he supports same-sex marriage," Mike Huckabee wrote in a fundraising appeal to supporters. "Nancy Pelosi immediately jumped on the announcement and emailed Democrat activists nationwide promising to continue their fight. This is going to be a defining issue this election. Obama, Pelosi and the Democrats have been a complete failure on economic issues so now they are going to focus on issues that will rile up their base. Well, Mr. President it's going to rile up our folks also. Men and women who support traditional marriage."

  • Rep. Bill Taylor

  • Deval Patrick

  • Frank Lautenberg

    "President Obama's support for marriage equality marks an important moment for civil rights in America," said Senator Frank R. Lautenberg (D-NJ), who co-sponsored legislation that would repeal the Defense of Marriage Act (DOMA). "We simply can not treat same sex couples as second-class citizens in our country. Marriage equality is one of the most significant civil rights battles of our time and is critical to guaranteeing the equal protection under the law promised to every American in the Constitution. The President's support for marriage equality should inspire Congress, Governors and state legislatures to advance civil rights for all Americans."

  • Allen West

  • Ann McLane Kuster

  • Sen. Patrick Leahy

  • Peter Welch

    "This is an historic moment and I applaud the President for his decision and courage," Rep. Peter Welch (D-Vt.) said. "One of the greatest and most liberating human emotions is acceptance. And what the President did today was accept that the quality of love two people share is more important than their gender. The President's decision required him look within and engage his heart. It is truly wonderful and welcome news."

  • Senator Patty Murray

  • Steve Rothman

    "As an early and strong proponent of Marriage Equality, I am very happy that President Obama has made this announcement," said Rep. Steve Rothman (D-N.J.) "Marriage Equality is a matter of basic human rights and all of America's same-sex families are now closer to having their unions recognized by our government. This is an important step in our country's march toward achieving true justice and equality for all."

  • Chuck Schumer

  • JackieForNH

  • Howard Dean

    "President Obama's public support for marriage equality is an historic affirmation of the fundamental American value of equal rights for all," said Howard Dean. "Having signed the nation's first law allowing Civil Unions as Governor of Vermont, I'm also proud to see our president affirm the belief that I and so many other Americans hold: loving and committed couples should have the same benefits that are extended through marriage. Marriage equality is a right and a benefit to all families."

  • Mike Quigley

  • Senator Ben Cardin

  • Sen. Barbara Boxer

  • Senator Dick Durbin

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