In these hyperbolic times, it's easy to fall into overstatement. Somehow, the farm-to-table dining preferences of Sarah Huckabee Sanders or the subliminal, sartorial messages of the first lady have become the subject of breathless debate. Cotton-candy controversies swirl for a moment and then disappear. The replacement of retiring Supreme Court Justice Anthony Kennedy is not like that. It is, to paraphrase former Vice President Joe Biden, a big doggone deal. So big that Biden's old boss, former President Barack Obama, has descended from his Olympian remove to fire up the troops Thursday. He urged Democrats to quit moping, avoid complacency...