On Sunday, Vice President Joe Biden seemed to signal a shift from the Obama Administration in its long-running (and somewhat tortured) approach to gay marriage.

“I am absolutely comfortable with the fact that men marrying men, women marrying women and heterosexual – men and women marrying – are entitled to the same exact rights, all the civil rights, all the civil liberties,” Biden said on “Meet the Press”. “And quite frankly, I don’t see much of a distinction beyond that.”

Rebecca Hickman, left, and Evan McDuff raise the Gay Pride flag in the front of the Fogler Library to mark the start of the annual Pride Week at the University of Maine on April 9.

“The Vice President has made similar comments many times before,” said Obama deputy campaign manager Stephanie Cutter in an interview Monday afternoon on MSNBC’s “Andrea Mitchell Reports”.

The whole kerfuffle over what Biden said (and meant) has re-opened a somewhat heated debate within Democratic circles: Why won’t President Obama simply come out in favor of gay marriage once and for all?

Obama, who supports civil unions but not same-sex marriage, has said repeatedly that the issue is very personal for him and acknowledged that he struggles with it. In an interview with liberal bloggers in the fall of 2010, Obama said he “wrestles” with the issue, adding: “I think it’s fair to say that it’s something that I think a lot about.”

His caution is due in no small part to politics — yes, there is politics in absolutely everything — although it’s not an easy political calculation to unravel.

Let’s start with the basics. Polling over time makes clear that public opinion is headed in the direction of legalizing gay marriage.

Here’s a chart the terrific Post polling unit put together detailing how people have answered the legal/illegal question on gay marriage since 2004.

Post Polling

Obama, himself, seems to be well aware of what he called the “arc of history” in that 2010 interview. “The one thing I will say today is I think it’s pretty clear where the trendlines are going,” said Obama at the time.

The trendline is clear. But so too is the fact that Obama would gain little — and could well lose out among a critical core constituency — if he came out in favor of gay marriage before the election.

Here’s why: While legalizing gay marriage is clearly becoming the majority position in the country, it’s not supported by the sort of large majorities that would impel Obama to action.

Combining results from three Post-ABC News polls between March 2011 and March 2012 that asked whether gay marriage should be legal, 52 percent said it should while 44 percent preferred it to stay illegal.

Among some key subgroups, the story was similar — majorities favored legalization but it was far from a slam-dunk result. Fifty three percent of white voters supported legalization while 43 percent opposed it; 57 percent of independents back making gay marriage legal while 40 percent were opposed. Voters aged 40-49 narrowly support legalization (52 percent) while those between the ages of 50-64 narrowly oppose it.

On the other hand, African Americans, one of the main pillars of the President’s political coalition, remain decidedly skeptical about gay marriage. In the last year’s worth of Post-ABC data, just 42 percent said they support legalization while 55 percent oppose it.

Viewed through that lens, coming out in support of gay marriage looks like an unnecessary political risk for Obama.

Yes, it would clearly thrill a portion of his base (gays and lesbians) but it could alienate — at least in parts — another portion of his base (African Americans) that he desperately needs to win reelection this fall.

And, it’s hard to see the LGBT community abandoning Obama — either for former Massachusetts governor Mitt Romney or to simply sit on the sidelines — given that the President can point to the repeal of “Don’t Ask, Don’t Tell” and the decision to stop defending the constitutionality of the Defense of Marriage Act as signs that he is working to address their concerns. (Cutter made mention of both moves to argue that the Obama Administration has a strong record on matters of gay rights.)

Simply put: The political upside of coming out in support of gay marriage is simply not as high as the political downside of coming out in support of gay marriage. Hence, the quick work of the Obama team to minimize Biden’s comments — and the fact that the Administration nas been decidedly low profile on a measure that would ban civil unions set to be voted on in North Carolina on Tuesday. (Make sure to read Amy Gardner’s terrific story on Obama’s delicate dance in the Tarheel State.)

“On any such issue that is not part of your game plan, the art of communications is limiting the time that it is a major issue that is moving you off your game plan or off your message,” explained Chris Lehane, a veteran Democratic communications consultant.

The other thing to consider when it comes to the politics of gay marriage is that while it might not be a slam dunk for Obama to be for it before November, it could well be just that sort of issue if he is elected to a second four-year term.

Why? Because the Post-ABC polling shows a huge generational divide — with young people overwhelmingly supportive of legalization. Fully 65 percent of people aged 18-29 say gay marriage should be legal while 61 percent of those aged 30-39 agree. And there is every indication that each younger generation feels increasingly comfortable with the idea of gay men and women being married.

Given those numbers, in even three years time — and unburdened from concerns about reelection — it’s not inconceivable (with apologies to Vizzini in “The Princess Bride”) to imagine that President Obama’s evolution on the issue will be complete.

But, that final step in the evolution simply will not happen between now and November.