When President Barack Obama announced an agreement to double fuel-economy requirements Friday, standing with him were industry executives and environmental, public health and labor leaders, all of whom, remarkably, had signed off on the deal. But the real credit for this historic achievement, which is expected to cut oil consumption by 1.5 million barrels per day and eliminate half of all carbon pollution nationwide, doesn't go to the White House. Instead, thank California. For decades the state has set the nation's clean-energy agenda; it's been the tip of the spear in the fight for higher fuel standards. Its huge automobile...