John Roberts' Shift Magnifies 2012 Stakes

In the wake of the health care ruling and the Arizona immigration ruling, it's official: "Chief Justice Roberts has become a 'swing' justice on the Supreme Court," concludes Clint Bolick in the Wall Street Journal. That means the court now has only three solid conservatives, to four solid liberals. Of course, because both swing votes, Roberts and Anthony Kennedy, lean right, the court is still "the most conservative in nearly a century," Bolick allows. But it means the conservative majority is suddenly fragile.

Now, if Obama replaces a single conservative justice, the court will turn "sharply to the left." Just look at the health care ruling: Roberts joined conservatives in saying that Congress couldn't penalize inaction under the Commerce Clause. "With the replacement of one conservative justice by a liberal, congressional power under the Constitution's Commerce Clause will be boundless," Bolick argues. With three justices in their 80s, whoever wins in November might well get that chance. (More US Supreme Court stories.)