But just as McCain has asked voters to check his opponents' track record, a glance at his is heartening.

McCain, unlike a number of fellow GOP senators, voted in favor of Ronald Reagan's failed nomination of Robert Bork to the Supreme Court. And as National Review Online's Jim Geraghty notes, McCain characterized as "a largely unknown quantity" George H.W. Bush's nomination of Justice David Souter — who now usually votes with the high court's liberal contingent.

We know that Sens. Clinton and Obama want the federal judiciary to be a liberal quasi-legislature. McCain this week committed himself to buttressing the federal courts' integrity as what they were meant to be: nonpolitical tribunals, dedicated to upholding the Constitution.