Imagine if this case ends up as a re-run of the ObamaCare ruling, with squishy Anthony Kennedy shocking everyone by joining the conservatives Scalia, Thomas, and Alito — only to have John Roberts form a majority with the Court’s four liberals. Old CW: Roberts is the worst Republican pick since Souter! New CW: Roberts is the worst Republican pick since Brennan!

Nah, just kidding. Rest assured, this morning’s lip service about “millennia” of tradition aside, Kennedy will be voting with the lefties this time. The only suspense is over whether it’ll be 5-4 or 6-3.

At the start of Tuesday’s arguments, Chief Justice Roberts said that he had looked up definitions of marriage and had been unable to find one written before a dozen years ago that did not define it as between a man and a woman. “If you succeed, that definition will not be operable,” the Chief Justice said. “You are not seeking to join the institution. You are seeking to change the institution.”

Justice Kennedy, who many consider the likely swing vote on the case, weighed in with skepticism as the advocates for gay marriage made their case. He said the definition of marriage “has been with us for millennia.”

“It’s very difficult for the court to say, ‘Oh, we know better,’ ” he said.

How do we know he’s not terribly serious about that? Because he’s dismissed arguments grounded in tradition in other landmark gay-rights cases. Hist most famous opinion for the court came in Lawrence v. Texas, a challenge to Texas’s law outlawing sodomy between gays. The Supreme Court had upheld a state sodomy ban less than 20 years earlier, in Bowers v. Hardwick. Needless to say, there’s lots and lots and lots of tradition behind criminalizing gay sex acts, both here in the U.S. and abroad, and backed by plenty of majority support historically. That didn’t stop Kennedy from striking down the Texas statute and tossing out the Court’s own precedent in Bowers on grounds that he and the rest of the majority did in fact “know better.” Why wouldn’t he do the same thing here? Also, while it’s true that Kennedy’s opinion in the Windsor case two years ago struck a federalist note in nuking part of DOMA because the states, not the feds, get to define marriage, it’s not true that Kennedy typically defers to state majorities in gay-rights cases. As I say, he tossed out a duly enacted sodomy statute in the Lawrence ruling on grounds that it violated the petitioner’s due process rights. Years earlier, in Romer v. Evans, he struck down a statewide popular referendum in Colorado as a violation of the petitioner’s right to equal protection. In matters of gay rights, when an individual runs up against a state law, Kennedy reliably sides with the individual. The point in Windsor about states getting to define marriage instead of the feds was really just his way of striking down part of DOMA without going the whole nine yards and finding that individuals have a right to gay marriage that neither their state government nor the federal government can deny. Kennedy knew he’d get to rule on that much broader question eventually, i.e. this summer. No need to rush into it.

In fact, the NYT notes that later in this morning’s oral arguments, Kennedy “expressed qualms about excluding gay families from what he called a noble and sacred institution.” Audio of the arguments has already been posted; there are more arguments set for this afternoon. I’ll update later if he says anything that suggest he’s showing his cards, but it would be one of the great shocks in modern American jurisprudence if this guy, given his track record of landmark libertarian-ish pro-gay rulings, suddenly turned around and stiffed lefties on the biggest gay-rights case of them all. Which raises an interesting strategic question, per SCOTUSblog: What will Roberts do if in fact Kennedy votes with the liberals to form a five-justice majority for legalizing SSM? By tradition, the chief justice gets to assign the opinion of the Court — if he’s in the majority. If he isn’t, the senior-most justice in the majority gets to assign it. In this case, that would be — ta da — Anthony Kennedy, who will almost certainly assign it to himself and write a sweeping capstone to the line of gay-rights rulings he’s authored. If Roberts prefers a ruling that’s narrower than what Kennedy has in mind, he could join the majority for strategic purposes, making it 6-3, and then assign the opinion to himself, crafting a more circumscribed opinion. Then again, notes SCOTUSblog, that might not achieve anything: If Kennedy decides to author his own much broader concurring opinion and gets the four liberals to join it, then his concurrence will have the force of law since it would still represent a majority of the Court. In which case, maybe Roberts is better off siding with the conservatives in the minority — assuming he agrees with them in the first place, that is.

Update: Are those cards showing?

The second half of today’s arguments dealt with whether a state that has banned gay marriage is constitutionally required to recognize a gay marriage performed in a state where it’s legal. The fact that Kennedy seemed less interested in that issue, says SCOTUSblog, may suggest that he thinks it’s moot — i.e. since he’s planning to make gay marriage legal everywhere as a matter of equal protection, we won’t have to worry about anti-SSM states refusing to recognize marriages performed elsewhere.