Even as Donald J. Trump trounced him from New Hampshire to Florida to Arizona, Senator Ted Cruz could reassure himself with one crucial advantage: He was beating Mr. Trump in the obscure, internecine delegate fights that could end up deciding the Republican nomination for president. “This is how elections are won in America,” Mr. Cruz gloated after walking away with the most delegates in Wyoming last month. Now, as he faces a potentially candidacy-threatening contest on Tuesday in Indiana — where a new NBC News/Wall Street Journal/Marist poll, released Sunday morning, showed him trailing Mr. Trump by 15 percentage points...
