For the sake of posterity, I think Roberts will also side with the left
So do I. Roberts has three abiding core values: conservatism, legacy and the integrity of the courts.
On the first count, Roberts would side with the conservatives. The latter two would compel him to side with the left and Kennedy.
I think if Roberts vote could change the outcome, he'd side with the conservatives. But it seems increasingly unlikely that his vote will change anything. Kennedy seems poised to side with the left on this issue and preserve gay marriage. So Roberts is left with his own personal legacy and the intergrity of the courts.
No one save Scalia wants to be this generations Leon Bazile;
Almighty God created the races white, black, yellow, malay and red, and he placed them on separate continents. And but for the interference with his arrangement there would be no cause for such marriages. The fact that he separated the races shows that he did not intend for the races to mix.
Judge Leon Bazile ruling against Mildred and Richard Loving
With 50 years of separation, Leon sounds ignorant as ****. And that ruling against the Lovings defines his legacy. I think Roberts recognizes the issue of gay marriage will be similarly important in the long term. With opposition to gay marriage look back upon and scorned as useless ignorance. I don't think he wants to be on the wrong side of this issue.
As for the integrity of the court, most of your major civil rights legislation was historically done as close to unanimous as possible. Both Brown v. The Board of Education and Loving V. Virginia ruling were unanimous. A deeply divided court makes the USSC look political. A more unanimous verdict, impartial and more constitutional. I see this ruling as being in the same ball park in terms of long term significance. I suspect this may push Roberts toward concurring sheerly for the sake of consensus within the courts.
I think its likely that we'll get a 6 to 3 ruling out of the court in favor of gay marriage. I'd say even 7-2 was possible....though quite unlikely. I don't see Scalia or Thomas siding with gay marriage regardless.
And as an aside, I disagree with Roberts on many issues. But I think he's a fine Chief Justice. Thoroughly qualified, thoughtful, and principled. I just disagree on where he's placed his principles.