The surprise endorsement of same-sex marriage on Sunday by Vice President Joe Biden is leading to some predictable election-year cynicism. Was this the Obama White House trying to have it both ways — sending a signal to gay supporters that the president will be with them in a second term while avoiding the risk of alienating social conservative supporters that would go with a direct statement of support from the president?

Our guess is not. If President Barack Obama was really trying to give a wink and a nod to supporters of marriage equality, Mr. Biden would be far from the ideal messenger. Although he is the second-highest elected official in the land, he is so gaffe-prone (remember the line from 2007 about his future boss being "articulate and bright and clean and a nice-looking guy"?) that he lacks much punch as a strategic leaker of the administration's intentions.

Moreover, although Mr. Biden made an eloquent explanation of his thinking on the matter, the context in which he placed his recent evolution on the issue was not the kind of story the White House would make up. Certainly, the anecdote about seeing the heart-melting "look of love" two young children of a gay couple had for their parents could have come from a focus group, but the fact that this meeting took place at a fund-raiser in a private home in Los Angeles — rather than, say, at a PTA meeting in Ohio — gives it a less-than-ideal authenticity.

In all, the appearance on NBC's "Meet the Press" on Sunday had the unmistakable air of Biden being Biden, an admirable habit of the vice president saying what he really thinks even when it makes the president uncomfortable. And on this topic, the president deserves to be made uncomfortable. Mr. Obama's description of his own views on same-sex marriage as "evolving" sounds too cute by half. Either he believes that all men and women should have the same state-sanctioned right to marriage, or he doesn't. Either he thinks that the children of gay and lesbian couples deserve the same protections as their peers, or he doesn't.

The effect of Mr. Biden's remarks may be a bit of a coming-out party for members of the administration; this morning, Education Secretary Arne Duncan made public his support for gay marriage in an interview on MSNBC. Housing Secretary Shaun Donovan had already said he supports marriage equality. Mr. Duncan said no one had ever asked him before, but now you can bet that every other high ranking White House official is going to be put on the spot. Pretty soon, Mr. Obama may be the lone holdout at cabinet meetings.

The president has long said he believes that gay couples should be offered the opportunity for civil unions that provide the same legal protections as marriage but with a different name. The Ninth Circuit Court of Appeals' recent ruling in the challenge to California's Proposition 8, which banned gay marriage in that state, convincingly made the case that such a position is constitutionally unsupportable. Since California already had a domestic partnership law, the court noted, the only effect of Proposition 8 was to deny same-sex couples the designation of "marriage." All of the public policy objections that gay marriage opponents raise (fallacious as they are) disappear in such a circumstance, and the fight then becomes merely about the use of a word. Denying gay couples a designation that is allowed for straight couples "serves no purpose, and has no effect, other than to lessen the status and human dignity of gays and lesbians in California, and to officially reclassify their relationships and families as inferior to those of opposite-sex couples," the Ninth Circuit ruled. "The Constitution simply does not allow for laws of this sort."

On other issues, President Obama has stood up for gay rights. He ended the pointless and discriminatory "don't ask, don't tell" policy that banned openly gay troops from serving in the military, and he has instructed the Justice Department to stop defending the Defense of Marriage Act, which bans federal recognition of gay marriages that are sanctioned by individual states. It is hard, then, to figure out why the president has been so tepid in his attitude toward the central equal rights question of the day. It is conceivable that he has religious objections to same-sex marriage, but on any number of other issues he has demonstrated ample understanding of the principle that religious belief alone is not a constitutional basis for the law.

The only other explanation is that his reluctance is political. Although recent national polls on the subject have found that supporters of same-sex marriage outnumber opponents (and in some surveys, constitute a clear majority), opposition tends to be higher among minority voters, who are crucial to the president's re-election chances. Perhaps Mr. Obama would prefer not to talk about it, but the time when a presidential candidate could sit on the sidelines of this issue has passed. Rather than scrambling to explain away another Joe Biden gaffe, the president should take the opportunity to lead.