Shortly after news networks said President Obama had won reelection, this photo was sent from the president’s Twitter account. The photograph was retweeted hundreds of thousands of times, becoming the most popular image in Twitter history. (Scout Tufankjian/Obama for America)

Who is embracing whom in that photograph of the Obamas that went viral on election night? The photograph, shot from below and isolating the first couple against a cloudy sky, shows the president embracing his wife at a campaign rally in August. The first lady is seen from behind, enclosed in the arms of the president, whose eyes are closed. Sent from the president’s Twitter account Tuesday night shortly after news networks declared him the winner, the photograph was immediately retweeted hundreds of thousands of times, making it the most popular image in Twitter history and propelling it to instant love across a host of social-networking programs.

It has all the generic ingredients of a successful political image. With its moody and slate-gray sky, it encapsulated the drama many of President Obama’s supporters felt Tuesday evening: The Obamas had weathered the storm. It also appealed to the almost cultlike sense of affection many Americans feel for the couple. Surging through social networks commonly used to keep people in touch with family and friends, it offered a sense of intimacy with the first family, stroking the same emotional receptors as photographs of the Obama daughters, Malia and Sasha, and the family’s dog, Bo. For Democrats, it also has a basic allegorical function: The bonds of love between Barack and Michelle Obama symbolize a healthy society. For African Americans, it adds to a repository of images that celebrate the success of the Obamas in opposition to the frequent demonization of supposedly dysfunctional black families in popular culture.

But the photograph has a remarkable and specific latent message, too. Unlike many images of political marriage in which the man lays claim to his wife through a symbolically possessive gesture — touching her shoulder, raising her hand up or kissing — the embrace between these two people seems mutual. The first lady is, among many other things, a big woman, famed for her well-toned arms, and in this image of hugging, she’s giving as good as she gets.

The president, if anything, seems to need this hug and appears almost dependent and vulnerable. The obligatory masculine markers of leadership — resolve, self-sufficiency and emotional equanimity — dissolve into the obliterating communion of two people lost in their own love world.

It’s impossible to know the reality behind this image, whether the president and the first lady are indeed in love in the way that photograph suggests. Perhaps this is just another very successful variation on the carefully staged depiction of love that is mandatory for political success. But regardless of the reality, that variation is significant. The photograph strongly suggests an ideal of mutuality in marriage, unencumbered by older ideas of possession and obedience that still hold sway in some deeply traditionalist religions.

Political rhetoric keeps those older ideas alive in vestigial but important ways. It’s a common joke, among politicians, to say that one’s spouse is “the best choice I ever made.” George W. Bush loved this line, and Mitt Romney reprised a version of it in his concession speech early Wednesday. It seems at first a mildly self-deprecating statement, flattering the man’s “better half.” But it also reinforces marriage as a man’s choice of a woman, and the politician as a decision maker. It is marriage cast in the active tense, with the man as subject of the sentence.

Videotape of the Dubuque, Iowa, campaign event in August at which the photograph was taken show plenty of small scenes of traditional political love: The president leaning in for a kiss, touching Michelle’s shoulder, walking hand in hand. But out of what must surely be thousands of images of the two together, the president chose this photograph to tweet, disseminating an image that emphasizes neither the man’s power nor the woman’s beauty. The image that went viral, that clearly speaks to people, represents a more modern ideal of true equality in emotional relations.

That it went viral on the same night that voters in four states broke with decades of anti-gay-marriage voting patterns and endorsed equality for same-sex couples may not be entirely accidental. Opponents of same-sex marriage often speak of the necessity of “defining” marriage in traditional terms, and anxiety about gay marriage is frequently expressed as a broader fear of redefining long-standing gender norms and categories. Conservative authors have produced books that decry the feminization of the American male, describing men as an endangered species.

The Obama photograph shows another reality, what might be called the limitless possibilities of true mutuality, of marriage beyond strict definitions. The Obama marriage appeals to many people, because it seems so comfortable, as if no one is worried about who wears the pants in the house, which is the reality of many healthy marriages today. In a healthy marriage, the partners don’t simply step into ancient gender roles and enact a drama of fidelity and obedience, they invent their own roles in the manner that serves both people best. Marriage is improvisatory, and every marriage is unique. Variation flourishes, and people work it out.

Among the many things that will come with a broader societal acceptance of same-sex marriage — which won at the ballot box for the first time since it emerged as a wedge issue in the 2004 reelection of President George W. Bush — is an extraordinary boon for straight men. The strictures of masculinity will likely fade as the fear of homosexuality abates, leaving more room for individual men to define their own notions of masculinity. That this photo became so popular at this particular moment suggests that we may be parsing the broader cultural implications of this election for a long time to come.