Justice Elena Kagan is now the junior-most justice of the U.S. Supreme Court. Justice Sotomayor no longer has to get the coffee and answer the door when the justices are in conference. It occurs to me that an interesting dynamic will now be taking place on the Supreme Court. With Justice Stevens' retirement, Justice Scalia is now the senior-most associate justice. This means, for the first time since 1969, the Chief Justice and the senior-most associate justice tend to vote together more often than not. Indeed, the next in line is Justice Kennedy, usually seen as a swing vote on the current Court, and then Justice Thomas, who also often votes with Chief Justice Roberts and Justice Scalia. It isn't until Justice Ginsburg, who comes next, that you get someone who typically votes on the other end from the Chief Justice.
Does this dynamic have any ultimate significance? Not immediately, since each vote counts just once. But the senior-most justice in the majority determines who writes the majority opinion. Usually that will be the Chief Justice in cases divided along ideological lines when Justice Kennedy sides with the conservatives. It's usually been Justice Stevens in cases when Kennedy sides with the liberals. So who will do so now? Not Justice Ginsburg. She's the senior-most among the four clear liberals. But four votes does not make a majority. She'd need a fifth vote to get a majority in cases involving all the justices, which would be most of them. That fifth vote will either be Justice Alito, who comes after her, or someone ahead of her in seniority, most often probably Justice Kennedy. In the 5-4 cases where Kennedy sides with the liberals, it will be Kennedy himself who determines who gets to write the majority opinion.
Before Justice Stevens' retirement, Justice Kennedy had a lot of power in ideologically-divided cases along the more typical lines. There are plenty of cases that don't go along such lines, but a good deal of the hot-button issues people who aren't serious court-watchers pay attention to involve 5-4 splits with Kennedy joining either the liberals or the conservatives. His power has come in being able to determine which side in such cases will win, sometimes using it to side partly with either side. But now he'll even get to decide who writes the opinion, and that gives him further power. Sometimes who writes the opinion affects quite a lot. It might affect which justices sign on to how much of the opinion, which doesn't usually affect the result but does often affect how much of the opinion becomes precedent for further cases and how broad a scope the opinion will be to affect other cases.
Sometimes it's in the best interests of ideological achievement of a majority to have the most moderate member of the coalition write the opinion. When Justice Breyer or Justice Ginsburg joins the conservatives, Chief Justice Roberts often will assign them the opinion, and he did the same with Justices Souter and Stevens. Justice Scalia has written several opinions when he's joined the liberals, and that would have been Justice Stevens' decision. But Justice Kennedy loves to write the hot-button opinions himself, so maybe he won't use this ability as fully as he could. Nonetheless, the justice who I happen to think is the most judicially-activist has been the most powerful member of the Supreme Court since Justice O'Connor retired, and now he's gained an ability that increases that power.