Donald Trump has had a good run of numbers lately. While his victory in New York this week was expected, he got 60 percent of the vote, more than the roughly 55 percent projected by the polls. He appears headed for victories in Maryland and Pennsylvania, which vote on Tuesday. He’s gained ground in California and is narrowly ahead of Ted Cruz in the first public polls of Indiana. He’s added about 2 percentage points over the past two weeks in our national polling average. But with Trump’s path to 1,237 delegates on such a knife’s edge, every percentage point...
