When asked about his views on same-sex marriage, Vice President Biden said he is “absolutely comfortable” with men marrying men and women marrying women. When Education Secretary Arne Duncan was asked Monday whether he thinks that same-sex couples should be able to marry, he said, “Yes, I do.”

The answer is apparently not as simple for President Obama.

As more top officials in his administration speak out in favor of same-sex marriage, Obama is facing increasing pressure to take sides in one of the most emotional and polarizing social policy debates of the modern era.

The president has said his views are “evolving,” but he has stopped short of the endorsements given by Duncan, Biden and Housing and Urban Development Secretary Shaun Donovan.

Several people close to the White House said the episode has exposed internal tensions within Obama’s team between those who want the president to say he favors same-sex marriage before the November election and others who worry about a political backlash if he does — not just among conservatives and working-class voters but among African Americans who are Obama’s most loyal support bloc but tend to oppose such unions.

About one in six of Obama’s top campaign “bundlers” are gay, according to a Washington Post review of donor lists, making it difficult for the president to defer the matter. Activists are planning a campaign for the adoption of a pro-gay-marriage plank in this year’s Democratic Party platform. And a series of referendums this year on same-sex marriage — including one in the swing state of North Carolina on Tuesday — are putting the issue at the forefront.

“It’s my understanding there are people in the campaign, the White House and the administration who are talking about what he will say if he is asked,” said Winnie Stachelberg, executive vice president of the liberal Center for American Progress and a senior advocate in the lesbian, gay, bisexual and transgender community.

The support from Biden and Duncan prompted Joe Solmonese, president of the Human Rights Campaign, to issue a statement declaring that there is “no doubt in my mind that the president shares these values” and calling on Obama to express himself.

Richard Socarides, a prominent gay activist who was President Bill Clinton’s top adviser on LGBT issues, said Monday that Obama and his team are “boxed in” on the marriage issue.

“It’s a problem of their own making,” he said. “The president’s ‘evolving strategy’ could maybe work for them as a stopgap, but you can’t be evolving on a significant national policy issue for two years, especially in a presidential election. I don’t think it serves him well. Really, as a political matter, it’s too cute.”

Strategists for presumptive Republican nominee Mitt Romney think that any sustained focus on same-sex marriage could help unite the conservative coalition behind his candidacy, particularly in key swing states such as Iowa, where the Republican Party remains deeply fractured after a bruising primary campaign.

And if Obama is portrayed as unsure on the issue, or does shift his views, it could undercut his efforts to paint Romney as a weak-kneed flip-flopper. The former Massachusetts governor appeared sensitive to that point Monday as he told an Ohio television reporter that he thinks marriage should be between a man and a woman.

“It’s a position I’ve had for some time, and I don’t intend to make any adjustments at this point — or ever, by the way,” he said.

White House and campaign officials argued Monday that, regardless of his views on marriage, Obama has amassed an unparalleled record on LGBT rights — signing a hate-crimes law, repealing the military’s “don’t ask, don’t tell” policy, pressing for hospital visitation rights for same-sex partners and declining to argue in court for the Defense of Marriage Act. But some gay activists have been frustrated by the president’s refusal to budge on the marriage question, as well as his aides’ recent announcement that he had no plans to sign an executive order prohibiting federal contractors from discriminating on the basis of sexual orientation or gender identity.

In his comments aired Sunday on NBC’s “Meet the Press,” which had been taped Friday, Biden spoke in personal terms at some length about the moment three weeks ago when he greeted a gay supporter and his children at a Los Angeles fundraiser.

“The good news is that, as more and more Americans come to understand, what this is all about is a simple proposition: Who do you love?” Biden said. “And will you be loyal to the person you love? And that’s what people are finding out. I[It’s] what all marriages at their root are about, whether they’re marriages of lesbians or gay men or heterosexuals.”

Gay rights activists hailed the vice president’s comments as a major milestone. The White House and the Obama campaign, however, sought to play down any perceived differences between Biden’s unequivocal support for same-sex marriage and Obama’s evolution.

Senior campaign aides quickly called leading LGBT activists to underscore that Biden’s remarks do not reflect any changes in position and that community leaders should temper their responses. Shortly thereafter, Biden’s office released a written statement saying that he was “expressing that he too is evolving on the issue, after meeting so many committed couples and families in this country.”

On Monday, White House press secretary Jay Carney told reporters during a contentious exchange that Biden’s comments were “completely consistent” with Obama’s views on the rights of same-sex couples. Carney argued that Biden had said his views were evolving, although reporters interjected to note that this came from the after-the-fact written statement.

“There is a little bit of an overreaction here,” Carney said.

Both Obama and Biden have focused heavily on raising money from gay donors, who make up a key component of the president’s fundraising base. Although many activists demand that Obama take a position firmly in favor of same-sex marriage, many of his top financial backers have struck a more pragmatic pose, urging patience and pointing to his policy successes.

“No one disputes that this guy has gotten more done for LGBT equality at the federal level than all 43 previous presidents combined,” said top Obama bundler Andrew Tobias, who serves as treasurer of the Democratic National Committee. “No one disputes that. Or that there will be further progress if he gets a second term.”

The Obama campaign has made an effort to reach out to gay donors, including scheduling regular fundraisers over the past year and creating an official finance committee for the lesbian, gay, bisexual and transgender community. Next month, the president is scheduled to travel to Los Angeles for a 700-person LGBT gala featuring the pop rock performer Pink.

Dana Perlman, a Los Angeles lawyer who serves as a co-chairman of Obama’s LGBT finance committee, said in an interview Monday that Obama is navigating a rapidly changing political landscape in which same-sex marriage is gaining approval much more quickly than expected. “I am looking forward to the day when the president completes his evolution,” Perlman said, but he added that he credits Obama with pushing the national debate forward.

“Marriage equality is, of course, one of the top issues for the LGBT community,” said Perlman, who has raised more than $500,000 for Obama’s campaign and is co-hosting the June LGBT fundraiser in Los Angeles. “It’s not the only issue, however.”

Chad Griffin, the incoming president of the Human Rights Campaign, was the one who posed the question to Biden at the recent Los Angeles fundraiser. He said in an interview Monday that he has repeatedly pressed Obama in private to support marriage equality and that the president is likely to get more questions at the June fundraiser.

As for White House efforts to equate Biden’s comments with the president’s views, Griffin added: “Only in Washington and in politics could one parse the words of the vice president. His words were very direct and clear and speak for themselves.”

Staff writers Philip Rucker and Ed O’Keefe contributed to this report.