Let's get this out of the way now: As far as big deals coming out of Washington, this year is already junked. With the midterm elections in view for jittery lawmakers, chances for a breakthrough on an immigration overhaul, a rewrite of the tax code, or a major jobs package have all but vanished. (Take a bow, partisans.) But we could wake up Nov. 5 with a very different political order. President Obama, at that point, would still have two years in the Oval Office to seal his legacy. Certainly the President himself will help shape that future. Beyond that,...