Reacting to President Obama's full "evolution" on gay marriage, prominent gay-rights advocates and others cheered the president's decision to offer public support. Obama's relationship with gay-rights advocates has been a sometimes rocky one. After pledging during the 2008 campaign to expand gay rights, advocates were dissatisfied with his slow movement on their key issues.

When Obama invited gay-rights activists to the White House for an LGBT reception, some of those activists grumbled on and off the record that Obama had shoved those promises aside. He chose to let Congress repeal " Don't Ask, Don't Tell ", and his Justice Department had defended the Defense of Marriage Act .

Gradually, Obama moved forward on those key issues: In a political victory for the president after the 2010 midterms, Congress did change military policy in December of that year, and in January 2012, Obama instructed the Justice Department to stop defending DOMA. Today, with Obama's public "evolution" complete (timeline here), advocates have the president's public support on their last major issue. They've offered praise in response.

Human Rights Campaign President Joe Solmonese released the following statement:

Today, President Obama made history by boldly stating that gay and lesbian Americans should be fully and equally part of the fabric of American society and that our families deserve nothing less than the equal respect and recognition that comes through marriage. His presidency has shown that our nation can move beyond its shameful history of discrimination and injustice.

In him, millions of young Americans have seen that their futures will not be limited by what makes them different. In supporting marriage equality, President Obama extends that message of hope to a generation of young lesbian, gay, bisexual and transgender Americans, helping them understand that they too can be who they are and flourish as part of the American community. And his words remind gay and lesbian families across the country, who, like their neighbors, struggle to afford healthcare and college for their kids, pay their taxes and plan for retirement -but with the added burden of discrimination- that they do not face those challenges alone and unheard.

Americans fundamentally believe in fairness, but many, like the President, have struggled to reconcile that core belief and the question of marriage equality. The President's words will no doubt inspire thousands more conversations around kitchen tables and in church pews.  We are confident that our nation will continue to move inexorably toward equality and we thank the President for so boldly leading us in that direction.

The Servicemembers Legal Defense Network has gained prominence in gay-rights activism over the past few years, through its efforts to repeal the military's "Don't Ask, Don't Tell" policy.  A statement from its president, Aubrey Sarvis:

This is a great day for gay and lesbian service members, who are living with the daily reality that while they are now be able to serve openly, they and their families are treated as second-class citizens under laws like the discriminatory Defense of Marriage Act (DOMA).

Certainly, the President's leadership in repealing 'Don't Ask, Don't Tell' laid the foundation for his reaching this positive outcome. We welcome the President's support for marriage and will work with him to repeal DOMA and all laws that undermine equality and treat our service members unfairly.

Evan Wolfson, founder and president of Freedom to Marry, a national umbrella group that supports state-level initiatives to legalize gay marriage, released this statement to reporters:

Today, President Obama added his voice to the growing chorus of Americans who believe that all loving and committed couples should share equally in the freedom to marry. Like so many others who have made this journey - from Bill Clinton to Laura Bush, most recently Vice President Biden, and a majority of the American people - President Obama has come to know loving and committed gay couples.

Through thought and conversation about these families and their dreams and challenges, President Obama has reflected on his own values of fairness and respect for others, and completed his journey to support for the freedom to marry.  He now becomes the first sitting President to join the  majority of Americans whose hearts have opened and minds have changed in favor of the freedom to marry.

The President's support marks a historic turning point for the freedom to marry movement. Yet there is much left to be done.  Forty-four states continue to exclude same-sex couples from marriage and because of the federal so-called  Defense of Marriage Act (DOMA), the civil marriages of thousands of same-sex couples are not respected by the federal government, thus depriving families of a crucial safety-net of federal protections and responsibilities.  It is time to repeal discriminatory laws that hurt families and help no one and speed passage of freedom to marry laws throughout the country. …

Ted Olson, the lawyer who represented George W. Bush in the 2000 election case and later served as Bush's solicitor general, later helped lead the court challenge to overturn California's gay-marriage ban, Proposition 8. Olson released a statement through the group that backed the court case, American foundation for Equal Rights:

"Today is a proud day for all Americans," said AFER lead co-counsel Theodore B. Olson.

"The bedrock American principles of freedom and human dignity are central to the political and legal convictions of Republicans, Democrats, liberals, and conservatives alike.  President Obama's words remind us that marriage and equality are universal values that unite us all.  They remind us that we are all-as a People and a Nation-striving to form a more perfect Union."

Gay-rights advocates weren't the only groups praising Obama. New York Mayor Michael Bloomberg weighed in:

This is a major turning point in the history of American civil rights. 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.