WASHINGTON -- Every sulfurous belch from the molten interior of the volcanic Trump phenomenon injures the chances of a Republican presidency. After Donald Trump finishes plastering a snarling face on conservatism, any Republican nominee will face a dauntingly steep climb to reach even the paltry numbers that doomed Mitt Romney. It is perhaps quixotic to try to distract Trump's supporters with facts, which their leader, who is no stickler for dignity, considers beneath him. Still, consider these: The white percentage of the electorate has been shrinking for decades and will be about 2 points smaller in 2016 than in 2012....