Based on oral arguments at the Supreme Court on Tuesday, it seems unlikely that there are five votes to recognize a constitutional right to same-sex marriage — the most sweeping option available to the nine justices, and the outcome many liberals and gay-rights supporters most want to see.

But those who support making same-sex marriage a constitutional right should, as the saying goes, be careful what they wish for. Analysts are already reading last rites to California's gay-marriage-barring Proposition 8 — the focus of Tuesday's Supreme Court hearing — but that would affect only California. If the Supreme Court rules that same-sex marriage is a right available to all Americans under the Constitution, on the other hand, that would invalidate the gay marriage bans on the books in 38 states. Here are four possible downsides to legalizing gay marriage — for its liberal supporters:

1. A judicial overreach could turn public opinion
Several of the justices on Tuesday — even some supportive of gay marriage — seemed wary of wading too deeply into the gay-marriage debate, preferring to let states and their citizens sort the issue out. Even before oral arguments began, the specter of the landmark 1973 abortion case Roe v. Wade loomed over the court, says Adam Liptak in The New York Times. "Judges, lawyers, and scholars have drawn varying lessons from that decision, with some saying that it was needlessly rash and created a culture war." Among the judges who are amenable to that view is liberal Justice Ruth Bader Ginsberg.

And the backlash against the Massachusetts Supreme Court's landmark decision to legalize gay marriage would seem to confirm these fears. That 2003 decision, making Massachusetts the first state in the U.S. to allow gay marriage, helped prompt 11 states to pass constitutional amendments barring same-sex marriage in 2004. (Eric Zorn at the Chicago Tribune argues against the backlash fears: "Gay marriage will not be the next 'abortion.'")

It could be that gay-marriage supporters will win in the end, says Paul Mirengoff at Power Line. "But a decent appreciation of democracy, human history, and the fallibility of the individual means that nine glorified lawyers shouldn't be the ones who make the change." It's ludicrous that "an institution that predates the United States by several millennia will be defined for a third of a billion people by whichever way Anthony Kennedy feels like swingin' that morning," agrees Mark Steyn at National Review. I mean, "why not ask Punxsutawney Phil?"

2. The GOP would have time to focus on other issues within its party
If the high court essentially legalizes gay marriage in America, and America goes along with it, "that would be a good thing for the GOP," says Elahe Izadi at National Journal. Right now, there's a big split in the Republican ranks on gay marriage, between older and socially conservative voters who oppose it and younger and libertarian voters who support it. "The Republican Party has to figure out a way to balance all those elements while also looking to attract new voters. A gay-marriage fight remaining front-and-center doesn't benefit the GOP."

On the other hand, if gay marriage remains illegal in 38 states, and public opinion keeps evolving, this is a huge opportunity for Democrats, says Chris Weigant at The Huffington Post. "Banning gay marriage has been a favorite for Republicans for the past 20 years," and a "proven winner," drawing conservative voters out to vote. But "in 2012, for the first time ever, gay marriage actually won at the ballot box, and in more than one state."

Conservatives are now a victim of their own success — there are barely any states left which haven't already banned gay marriage. And if gay marriage is already banned, then putting it back on the ballot is pointless, for conservatives. However, it is not going to be pointless for liberals, from here on out.... Progressives will be the ones putting gay marriage on the ballot from now on — in states where they have a good chance of the public voting for legalization. What used to be a wedge issue for conservatives will now cut the other way. [Huffington Post]

Unless the Supreme Court takes the issue off the table.

3. Sexual freedom could actually come to an end
The victory of gay marriage is also a big win for "bourgeois repression" — and a defeat for "sexual freedom," says Megan McArdle at The Daily Beast. "That's right, I said it: This is a landmark victory for the forces of staid, bourgeois sexual morality."

Once gays can marry, they'll be expected to marry. And to buy sensible, boring cars that are good for car seats. I believe we're witnessing the high water mark for "People should be able to do whatever they want, and it's none of my business." You thought the '50s were conformist? Wait until all those fabulous "confirmed bachelors" and maiden schoolteachers are expected to ditch their cute little one-bedrooms and join the rest of America in whining about crab grass, HOA restrictions, and the outrageous fees that schools want to charge for overnight soccer trips....

Of course, predictions are hard, especially about the future. Nonetheless, here is mine: whatever the Supreme Court decides, gay marriage will soon be legal throughout the land. But this will not mean that we drive ever onwards toward greater sexual freedom — rather, it will mean quite the reverse. The sexual revolution is over. And the revolutionaries lost. [Daily Beast]

4. Bill O'Reilly is now on your side
Raise your hand, liberals, if you ever expected to hear this argument from Fox News' highest-rated pundit:

The compelling argument is on the side of homosexuals. That's where the compelling argument is. "We're Americans, we just want to be treated like everybody else." That's a compelling argument. And to deny that, you've got to have a very strong argument on the other side. And the other side hasn't been able to do anything but thump the Bible. [Fox News, via Real Clear Politics]

In this segment, O'Reilly's actually to the right of Fox News' Megyn Kelly. And O'Reilly concludes his (lukewarm) embrace of gay marriage on this gracious note: "I want all Americans to be happy, I do." If the left can't disagree with Fox News, what's the point of politics?