President Barack Obama's announcement that he supports gay marriage is a heartening development in the campaign for equality, and it is commendable that he made his view public before the November election rather than afterward. But he needs to do more. Gay marriage won't be the central issue in his campaign against Republican Mitt Romney — the economy remains the foremost issue for voters — but the president needs to continue speaking out about the topic nonetheless. Voters in Washington, Maine and, most likely, Maryland will be voting on the issue this fall, and the president has the opportunity to play a meaningful role in those decisions, particularly here. If the president believes allowing marriage equality is a matter of fundamental justice, it is his duty as the nation's top elected official to do what he can to advance the cause.

Mr. Obama has long supported civil unions as an alternative to same-sex marriage, and he told ABC News in an interview today that his reluctance to support full marriage rights had been rooted in an understanding that "for a lot of people, the word 'marriage' evokes very powerful traditions, religious beliefs." However, he said that he has come to believe civil unions are not sufficient recognition for the committed, loving, monogamous relationships of those gay couples he sees in his personal and professional life.

That places him in an ideal position to speak to the large number of same-sex-marriage opponents who support gay rights in general, who do not consider themselves homophobic, but who remain uncomfortable with the idea of sanctioning gay unions as "marriage." It is a position that many African-American voters find themselves in, and they may be the key voting bloc if the issue comes before Maryland voters this fall. It is doubtful that many people will support gay marriage just because President Obama says so, but it is possible that he could persuade some of them by relating the story of his own evolving views.

The nation's views on gay marriage are evolving rapidly, too. Polls now consistently show that more people support gay marriage than oppose it, but that was not close to true even two years ago. The nation's last Democratic president, Bill Clinton, signed the Defense of Marriage Act in the heat of his re-election campaign in 1996. Yet last weekend, it was his recorded voice that urged North Carolina voters to reject a constitutional ban on gay marriage.

That vote — an overwhelming, 61-39 decision in favor of the ban — shows that the way forward for marriage equality is not going to be easy. So far, every state that has held a vote on gay marriage has rejected it. But Maryland could be the place where that streak ends, and President Obama can help. Talking about the issue might not do much to advance his electoral prospects (though it probably wouldn't hurt them much either). But it could do a great deal to advance the cause of justice.