One of the vacancies Democrats are trying to fill used to be held by John Roberts. After he became chief justice, Bush nominated the impeccably qualified Peter Keisler for the spot. The Democrats filibustered him, and the seat has gone empty ever since. A reasonable case can be made against filibustering judicial nominations, or for it. What can’t reasonably be argued is that Democrats should be able to use the tactic to keep a judgeship open until they have the power to fill it with a liberal, at which point Republicans have to stand down.