The Supreme Court stakes in 2012

The upshot is that Chief Justice Roberts has become a “swing” justice on the Supreme Court—along with Justice Kennedy, who has occupied the swing position held by Justice Sandra Day O’Connor until she was replaced by conservative Justice Samuel Alito in 2006. The court now is composed of three solid conservatives and four solid liberals, with Chief Justice Roberts and Justice Kennedy leaning conservative. …

That may be about to change. Three justices—liberal Ruth Bader Ginsburg and conservatives Antonin Scalia and Justice Kennedy—will reach their 80s during the next presidential administration. So whoever wins in November likely will have the chance either to reinforce the conservative majority, or to alter the court’s balance for the first time in nearly a generation.

The stakes never have been higher. First, because as human longevity increases, lifetime tenure has grown increasingly valuable. The average tenure of a Supreme Court justice today is 25 years—spanning more than six presidential terms. And presidents are catching on, naming ever-younger justices. If the newest justice, Elena Kagan, serves for all of her current life expectancy, she will remain on the court until 2045.