Californians know a few things. Two wrongs don’t make a right. Do unto others, and all that. But they also recognize how a turnabout can be fair play. And they’re ready, it seems, to fight fire with fire. Apologies for the aphorism storm. But it seems to sum up where America’s most-populous state stands this morning, as voters cast the final votes on a ballot measure that both sides argue will determine the future of democracy. And a few other small matters. Proposition 50 amounts to a highly partisan back-atcha. Approval of the measure will redraw the state’s congressional district...