"I would prefer not to." That was the invariable reply of the title character of Herman Melville's 1853 story "Bartleby, the Scrivener," when asked by his employer to perform a task. It's also a phrase you might use to describe the opinion of the Supreme Court in its latest redistricting -- or gerrymandering -- case, Gill v. Whitford. This was expected to be a closely divided case and one that many observers hoped would establish a clear legal standard to overturn partisan gerrymanders. But all nine justices concurred in the central point of Chief Justice Roberts' opinion, that the plaintiffs...