A man reaches out to a large rainbow flag placed in support of gay marriage in front of the U.S. Supreme Court last month. (ASTRID RIECKEN/For The Washington Post)

You may not have realized it, but a large cohort of Americans did something brave this month. For years — in some cases, decades — these lonely, marginalized souls had repressed their shameful feelings, hiding them from the world.

Then May came along, and they finally decided to come out of the closet.

As liberals.

That’s right: A large chunk of Americans recently decided to come out as “liberal” — socially liberal, to be specific. As a result, for the first time on record, self-proclaimed social liberals are no longer outnumbered by their conservative counterparts.

That's according to a new Gallup poll that finds the shares of American adults considering themselves "socially liberal" and "socially conservative" each total 31 percent. (The remaining respondents either called their views "moderate" or had no opinion.) Gallup has been tracking these categories since 1999, and the latest numbers simultaneously signify the highest share ever recorded for liberals and the lowest recorded for conservatives.

What explains this shift? Are Americans’ views on social issues becoming more liberal, or is “liberal” just getting a bit of brand revival?

In short, it’s probably both.

On multiple social issues, Americans have indeed become more likely to adopt the standard lefty stance. A record 60 percent now supports same-sex marriage, Gallup found, up from 37 percent a decade ago. Support for gay marriage has reached new highs for Democrats, independents and Republicans alike.

The trend is similar on drug policy. A majority of Americans now favors legalizing marijuana, concurrent with state-level decisions to decriminalize the drug. Abortion appears to be the outlier, however, with views bouncing around a bit; "pro-choice" and "pro-life" have taken turns holding pluralities in recent years.

But there’s reason to believe that the liberal marque has improved, too.

For closeted liberals, it's been a traumatic few decades since 1960, when John F. Kennedy memorably declared himself proud to be a liberal. He painted an idyllic portrait of what the term meant: "someone who looks ahead and not behind, someone who welcomes new ideas without rigid reactions, someone who cares about the welfare of the people — their health, their housing, their schools, their jobs, their civil rights, and their civil liberties."

But even then liberals were on the defensive — Kennedy’s speech was an answer to suggestions from his opponents that “liberal” should be understood as a pejorative. And the term’s potency as an insult would only grow, with Ronald Reagan and George H.W. Bush portraying the term as so repellent that it required the faux-euphemism “L-word” instead.

Kennedy's ideological heirs were less likely to defend the label, as well as the views that typically accompany it. Michael Dukakis insisted that the more pertinent L-word of his 1988 presidential candidacy was not "liberal" but "leadership." Bill Clinton studiously avoided being seen as too liberal, instead "triangulating" to render himself a more centrist voice. Subsequent politicians who wanted to portray themselves as more left-leaning than Clintonian centrists remained squeamish about the L-word, shifting instead to the inconsistently defined near-synonym "progressive" (even though "progressive" arguably carries worse historical baggage than ­"liberal").

But something seems to have changed in the past few years. Maybe it's the recent association of the "L-word" with a TV show about hot lesbians; maybe it's the effect of a flood of political love letters to liberty and libertarianism, cognates that may have reduced the toxicity of "liberal"; or maybe it's revulsion to some of the self-anointed standard-bearers of social conservativism who subsequently turned out to be bigots or hypocrites, or both. (Remember, part of the reason social liberals have come to match social conservatives in numbers is that the latter group has shrunk.)

Whatever the cause, people who seem to have always held more liberal political views — that is, Democrats — have become increasingly likely to embrace “liberal.” Also this month, for the first time since Gallup began keeping track, a majority of Democrats and those who lean Democratic identified their social ideology as liberal. It’s hard to believe that this shift — up from just 37 percent in 2010 — was driven entirely by new policy preferences.

On economic issues, mind you, Americans still call themselves conservative rather than liberal by a wide margin (39 percent to 19 percent). Yet that gap is shrinking, too, and is lower today than at any point since Gallup began keeping track in 1999. No wonder Hillary Clinton seems to be veering left; her weather vane has always been better calibrated than most.

Read more on this topic:

Greg Sargent: The real reason Hillary is embracing liberal positions

Eugene Robinson: GOP candidates swim against tide on gay marriage

Kimberly Hartke: Marijuana is the bomb