Statistics from Roberts’ first dozen terms on the high court show a growing willingness to be less doctrinaire in his conservatism — particularly in order to agree with Justice Anthony Kennedy.
For his first eight terms on the court, Roberts agreed most with Justice Samuel Alito (one of the staunchest conservatives on the court), according to statistics compiled by SCOTUSblog.
For three of the past four terms, he agreed most with Kennedy.
(The SCOTUSblog statistics lay out the percentages of times when the justices agreed with one another on three levels: (1) agree in part, all, or judgment; (2) agree in part or all; and (3) full agreement.)
It’s not just that Roberts is agreeing more with Kennedy; he’s agreeing with some of the more liberal justices more and the more conservative justices less.
In three of those recent terms, Roberts agreed with Justice Stephen Breyer, at least in judgment, in the same percentage of cases as he agreed with one of the more conservative justices (Alito twice and Justice Clarence Thomas once). In two terms, he agreed with Justice Elena Kagan more than he did with one of the more conservative justices (Alito in one instance and Thomas in another).
(This is not necessarily all Roberts’ doing. Breyer is by no means an unbending liberal vote on the court, and Kagan has shown a similar tendency in her time on the court.)
Some major caveats are in order. Inferring ideology from justice vote pairings, like any ideological measure of Supreme Court opinions, tends to be a volatile measure in small samples, because a different mix of issues will produce different coalitions. And Scalia’s sudden death makes both the 2015 and 2016 somewhat anomalous, so I’d be extra careful into reading anything into apparent shifts. If the trend seems to hold up after this term, though, I think you’d have something, and at least it bears watching.