Alternate headline: “Wait, Hillary wasn’t already on record in favor of gay marriage?” Evidently not. Five years ago, top-tier Democratic candidates concluded that they couldn’t safely support SSM publicly; five years and a double-digit swing in public opinion later, they’ve concluded that they can’t safely oppose it. The GOP will wrestle with this issue for awhile but, as of now, I think supporting gay marriage has reached the same stature among Democrats as supporting abortion rights. Namely, while occasional disagreement from backbenchers will be grudgingly tolerated in the name of winning purple states, no party nominee will ever, ever again end up on the other side of this issue. If you want to win a national Democratic primary, you’re pro-gay marriage, period. Hillary’s just checking the box.

In fact, it’s revealing that this is the first move she’s made politically since retiring from diplomacy. So orthodox has the party become on this subject that it might have been a liability for her if she had waited any longer before issuing her inevitable endorsement. (Bill “evolved” on the issue more than three years ago and published an op-ed just last week denouncing the Defense of Marriage Act, which of course he signed into law.) And don’t think she and her camp don’t know it. This announcement has been in the works for months, per this Politico report from November.

But according to two sources, Clinton’s aides have privately indicated to people that she will end up where her husband and daughter, Chelsea, have emerged on the issue – in favor of same-sex nuptials.

Her circle has “indicated privately that she feels like … because of her role as the country’s chief diplomat that it was appropriate for her to stay out of this” over the last two years, said one source, who added that the message was also that as soon as she’s left Foggy Bottom “and she’s given the right opportunity, that she will end up with the rest of her clan.”

Watch and you’ll see her explain that her perspective changed in part because of her friendships with gays. That’s basically the same rationale Rob Portman gave to support his own switch on this issue, and the left spent the entire weekend sneering at him for it. They won’t sneer at Hillary, but there’s some consistency in that: After happily tolerating Obama lying to their faces about his stance on gay marriage in the interest of getting elected, they’re not about to hassle Hillary. As long as you get to the right outcome, you’ve got carte blanche on how you get there. If you’re a Democrat.

Exit question via DrewM: Which position on this subject will the next GOP nominee take? Under normal circumstances, I’d bet the farm that he/she would punt by backing a federalist approach. But that’s not on the menu if, as expected, the Supreme Court strikes down gay-marriage bans as a violation of equal protection. Social cons will want the nominee to back a Federal Marriage Amendment overturning the decision even though it has zero change of passing. The party leadership will want the nominee to stay far, far away from that for fear of alienating young voters. What’s the solution?

Update: WaPo/ABC is out with a new poll finding record support for gay marriage at 58 percent. Here are the numbers among religious groups. The first column is the number in favor today, the second is the number in favor in 2004.

Another interesting result: “This poll suggests that the high court is the right place for it: Americans by nearly 2-1, 64-33 percent, say the legality of gay marriage ‘should be decided for all states on the basis of the U.S. Constitution’ rather than by each state making its own law on the issue.” I’m skeptical of that, but if it’s true then there’ll be less of a popular backlash after the Supreme Court rules than I thought.